INT 1A - PCI BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. v2.0c+ - READ CONFIGURATION DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address. (VIA Technologies devices)
	AX = B10Ah subfn 1106h
	BH = bus number
	BL = device/function number (bits 7-3 device, bits 2-0 function)
	DI = register number (0000h-00FFh) (see #00878)
Return: CF clear if successful
	    ECX = dword read
	CF set on error
	AH = status (00h,87h) (see #00729)
	EAX, EBX, ECX, and EDX may be modified
	all other flags (except IF) may be modified
Notes:	this function may require up to 1024 byte of stack; it will not enable
	  interrupts if they were disabled before making the call
	the meanings of BL and BH on entry were exchanged between the initial
	  drafts of the specification and final implementation
SeeAlso: AX=B10Ah,AX=B10Ah/SF=8086h



Format of Via Technologies' VT82C580VPX CPU-PCI bridge configuration:
Offset	Size	Description	(Table 00982)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 1106h, device ID 0585h)
 40h 16 BYTEs	unused
 50h	BYTE	cache control 1
 51h	BYTE	cache control 2
 52h	BYTE	non-cacheable control
 53h	BYTE	system performance control
 54h	BYTE	non-cacheable region 1 (high)
 55h	BYTE	non-cacheable region 1 (low)
 56h	BYTE	non-cacheable region 2 (high)
 57h	BYTE	non-cacheable region 2 (low)
 58h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. configuration 1
 59h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. configuration 2
 5Ah  6	BYTEs	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. row N ending address (N=0-5)
 60h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. type
 61h	BYTE	shadow RAM(Random Access Memory)	See also DRAM, SRAM. control 1
 62h	BYTE	shadow RAM(Random Access Memory)	See also DRAM, SRAM. control 2
 63h	BYTE	shadow RAM(Random Access Memory)	See also DRAM, SRAM. control 3
 64h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. reference timing
 65h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. timing control 1 (see #00996)
 66h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. timing control 2 (see #00997)
 67h	BYTE	32-bit DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. width (see #00998)
 68h	BYTE
 69h	BYTE	reserved ("do not program")
 6Ah	BYTE	refresh counter
 6Bh	BYTE	refresh control
 6Ch	BYTE	SDRAM control
 6Dh	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. control drive strength
 6Eh  2 BYTEs	reserved
 70h	BYTE	PCI buffer control
 71h	BYTE	CPU-to-PCI flow control 1
 72h	BYTE	CPU-to-PCI flow control 2
 73h	BYTE	PCI master control 1
 74h	BYTE	PCI master control 2
 75h	BYTE	PCI arbitration 1
 76h	BYTE	PCI arbitration 2
 77h	BYTE	reserved for chip test
 78h 136 BYTEs	reserved
!!!via\580vpx.pdf
SeeAlso: #00817


Format of AMD-640 System Controller:
Offset	Size	Description	(Table 00983)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 1106h, device ID 0595h)
 0Dh	BYTE	latency timer (bits 7-3)
		00h = 32*8 PCI clocks
		01h = 1*8 PCI clocks
		N = N*8 PCI clocks
 40h 16 BYTEs	unused???
 50h	BYTE	cache control 1 (see #00984)
 51h	BYTE	cache control 2 (see #00985)
 52h	BYTE	non-cacheable control (see #00986)
 53h	BYTE	system performance control (see #00987)
 54h	WORD	non-cacheable region 1 (see #00988)
 56h	WORD	non-cacheable region 2 (see #00988)
 58h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. configuration register 1 (see #00989)
 59h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. configuration register 2 (see #00990)
 5Ah  6	BYTEs	end of DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. banks 0-5
		each register specifies bits 29-22 of the bank's ending address
 60h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. type (see #00991)
 61h	BYTE	shadow RAM(Random Access Memory)	See also DRAM, SRAM. control register 1 (see #00992)
 62h	BYTE	shadow RAM(Random Access Memory)	See also DRAM, SRAM. control register 2 (see #00993)
 63h	BYTE	shadow RAM(Random Access Memory)	See also DRAM, SRAM. control register 3 (see #00994)
 64h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. timing (see #00995)
 65h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. control register 1 (see #00996)
 66h	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. control register 2 (see #00997)
 67h	BYTE	32-bit DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. width control register (see #00998)
 68h  2 BYTEs	reserved
 6Ah	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. refresh counter (in units of 16 CPU(Central Processing Unit) The microprocessor which executes programs on your computer. clocks)
 6Bh	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. refresh control register (see #00999)
 6Ch	BYTE	SDRAM control register (see #01000)
 6Dh	BYTE	DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. drive strength control register (see #01001)
 6Eh	BYTE	ECC control register (see #01002)
 6Fh	BYTE	ECC status register (see #01003)
 70h	BYTE	PCI buffer control (see #01004)
 71h	BYTE	CPU-to-PCI flow control 1 (see #01005)
 72h	BYTE	CPU-to-PCI flow control 2 (see #01006)
 73h	BYTE	PCI target control (see #01007)
 74h	BYTE	PCI initiator control (see #01008)
 75h	BYTE	PCI arbitration control 1 (see #01009)
 76h	BYTE	PCI arbitration control 2 (see #01010)
 77h 137 BYTEs	reserved
Note:	the AMD-640 uses PCI configuration mechanism #1; bus/device/function
	  are always 00h/00h/00h
SeeAlso: #00817,#01011


Bitfields for AMD-640 CacheCaching is a method of increasing performance by keeping frequently-used data in a location which is more quickly accessed. The most common caches are disk caches (store disk sectors in RAM) and RAM caches (store portions of main memory in special high-speed RAM which may be accessed as fast as the CPU is capable of accessing memory). See also Delayed Write, Write-Through. Control Register 1:
Bit(s)	Description	(Table 00984)
 7-6	cache enable
	00 disabled
	01 initialization (BIOS(Basic Input/Output System) A set of standardized calls giving low-level access to the hardware.  The BIOS is the lowest software layer above the actual hardware and serves to insulate programs (and operating systems) which use it from the details of accessing the hardware directly. fills L2 cache to known state)
	10 enabled (normal operation)
	11 reserved
 5	reserved (do not change)
 4-3	tag configuration
	00 eight tag bits, no "modify" bit
	01 seven tag bits, one modify bit
	10 ten tag bits, no modify bit
	11 nine tag bits, one modify bit
 2	reserved (0)
 1-0	type of cache RAM(Random Access Memory)	See also DRAM, SRAM.
	00 none
	01 reserved
	10 burst SRAM(Static Random Access Memory)  RAM which typically consists of one flip-flop per bit of memory.  Unlike DRAMs, static RAM retains its contents as long as power is applied.  Because there is no need to refresh the contents of memory addresses which are read, SRAM is faster than DRAM, but it is more expensive and typically is available in much smaller sizes than DRAM because each bit occupies more space on the chip.  See also DRAM.
	11 pipeline burst SRAM(Static Random Access Memory)  RAM which typically consists of one flip-flop per bit of memory.  Unlike DRAMs, static RAM retains its contents as long as power is applied.  Because there is no need to refresh the contents of memory addresses which are read, SRAM is faster than DRAM, but it is more expensive and typically is available in much smaller sizes than DRAM because each bit occupies more space on the chip.  See also DRAM.
SeeAlso: #00983,#00985


Bitfields for AMD-640 CacheCaching is a method of increasing performance by keeping frequently-used data in a location which is more quickly accessed. The most common caches are disk caches (store disk sectors in RAM) and RAM caches (store portions of main memory in special high-speed RAM which may be accessed as fast as the CPU is capable of accessing memory). See also Delayed Write, Write-Through. Control Register 2:
Bit(s)	Description	(Table 00985)
 7-6	reserved (0)
 5	backoff processor until L2 cache filled
 4	reserved (0)
 3	two banks of SRAM(Static Random Access Memory)  RAM which typically consists of one flip-flop per bit of memory.  Unlike DRAMs, static RAM retains its contents as long as power is applied.  Because there is no need to refresh the contents of memory addresses which are read, SRAM is faster than DRAM, but it is more expensive and typically is available in much smaller sizes than DRAM because each bit occupies more space on the chip.  See also DRAM. instead of one
 2	reserved (0)
 1-0	L2 cache size
	00 = 256K
	01 = 512K
	10 = 1M
	11 = 2M
SeeAlso: #00983,#00984,#00986


Bitfields for AMD-640 Non-Cacheable Control Register:
Bit(s)	Description	(Table 00986)
 7	segment C000h-C7FFh cacheable and write-protected
 6	D000h-DFFFh cacheable and write-protected
 5	E000h-EFFFh cacheable and write-protected
 4	F000h-FFFFh cacheable and write-protected
 3	reserved (0)
 2	force L2 cache fill
 1	reserved (1)
 0	L2 write mode (0 = writeback, 1 = write-through)
SeeAlso: #00983,#00985,#00987


Bitfields for AMD-640 System Performance Control Register:
Bit(s)	Description	(Table 00987)
 7	enable read-around-write
 6	enable cache read pipeline cycle
 5	enable cache write pipeline cycle
 4	enable DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. pipeline cycle
 3	enable PCI Peer Concurrence (PCI initiator can transfer to another
	  PCI device without blocking memory or CPU(Central Processing Unit) The microprocessor which executes programs on your computer. bus)
 2-0	reserved (0)
SeeAlso: #00983,#00986


Bitfields for AMD-640 Non-Cacheable Region register:
Bit(s)	Description	(Table 00988)
 15-11	bits 20-16 of region's base address
 10-8	size of non-cacheable area
	000 disabled
	001 = 64K
	010 = 128K
	...
	110 = 2M
	111 = 4M
 7-0	bits 28-21 of region's base address
SeeAlso: #00983,#00989


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Configuration Register 1:
Bit(s)	Description	(Table 00989)
 7-5	type of address mapping for memory banks 0 and 1
	---EDO/FastPageMode---
	000 eight-bit column address
	001 nine-bit column address
	010 ten-bit column address
	011 eleven-bit column address
	100 twelve-bit column address
	other reserved
	---SDRAM---
	0xx = 16-Mbit SDRAM (see #00991)
	1xx = 64-Mbit SDRAM
 4	reserved (0)
 3-1	type of address mapping ofr memory banks 2 and 3
 0	reserved (0)
SeeAlso: #00983,#00990


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Configuration Register 2:
Bit(s)	Description	(Table 00990)
 7-5	type of address mapping for memory banks 4 and 5 (see #00989)
 4-3	reserved (0)
 2-0	last populated memory bank
	000 - 101 = Bank0 - Bank5
	110,111 reserved
Note:	banks 2-4 are non-cacheable if tag RAM(Random Access Memory)	See also DRAM, SRAM. is ten bits + modified bit
SeeAlso: #00983,#00989


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Type register:
Bit(s)	Description	(Table 00991)
 7-6	reserved
 5-4	type of DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. in banks 4 and 5
	00 fast page mode (FPM)
	01 extended data out (EDO)
	10 reserved
	11 synchronous DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. (SDRAM)
 3-2	type of DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. in banks 2 and 3
 1-0	type of DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. in banks 0 and 1
SeeAlso: #00983,#00989,#00990


Bitfields for AMD-640 Shadow RAM(Random Access Memory)	See also DRAM, SRAM. Control Register 1:
Bit(s)	Description	(Table 00992)
 7-6	segment CC00h-CFFFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
	00 shadowing disabled
	01 write enabled
	10 read enabled
	11 both read and write enabled
 5-4	segment C800h-CBFFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
 3-2	segment C400h-C7FFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
 1-0	segment C000h-C3FFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
SeeAlso: #00983,#00993,#00994


Bitfields for AMD-640 Shadow RAM(Random Access Memory)	See also DRAM, SRAM. Control Register 2:
Bit(s)	Description	(Table 00993)
 7-6	segment DC00h-DFFFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
	00 shadowing disabled
	01 write enabled
	10 read enabled
	11 both read and write enabled
 5-4	segment D800h-DBFFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
 3-2	segment D400h-D7FFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
 1-0	segment D000h-D3FFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
SeeAlso: #00983,#00992,#00994


Bitfields for AMD-640 Shadow RAM(Random Access Memory)	See also DRAM, SRAM. Control Register 3:
Bit(s)	Description	(Table 00994)
 7-6	segment E000h-EFFFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
	00 shadowing disabled
	01 write enabled
	10 read enabled
	11 both read and write enabled
 5-4	segment F000h-FFFFh shadow RAM(Random Access Memory)	See also DRAM, SRAM. control
 3-2	ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. memory hole
	00 none
	01 = 512K-640K
	10 = 15M-16M
	11 = 14M-16M
 1	enable SMI redirection
	if set: 30000h-3FFFFh redirected to B0000h, 40000h-4FFFFh to A0000h
 0	redirect video RAM(Random Access Memory)	See also DRAM, SRAM. accesses (A0000h-BFFFFh) to system DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. rather than
	  PCI bus (used to initialize SMRAM at B0000h)
SeeAlso: #00983,#00992,#00993


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Timing register:
Bit(s)	Description	(Table 00995)
 7-6	RAS# precharge time
	00 = 2T (for 50ns DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM.) [T = HCLK period]
	01 = 3T (60ns)
	10 = 4T (70ns)
	11 = 6T
 5-4	RAS# pulse width
	00 = 3T (for 50ns DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM.)
	01 = 4T (60ns)
	10 = 5T (70ns)
	11 = 6T
 3-2	CASsee Communicating Applications Specification# pulse width
	FPM: 00=1T, 01=2T, 10=3T, 11=4T
	EDO: 00=4T, 01=1T, 10=2T, 11=3T
 1	write pulse width (0 = 1T, 1 = 2T)
 0	delay from column address to CASsee Communicating Applications Specification# (0 = 1T, 1 = 2T)
SeeAlso: #00983,#00994


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Control Register 1:
Bit(s)	Description	(Table 00996)
 7-6	page mode control
	00 close page after access
	01 reserved
	10 keep page open until timeout or page miss
	11 close page if processor has not accessed DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. for 8 CPU(Central Processing Unit) The microprocessor which executes programs on your computer. cycles
 5	enable fast DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. decoding
 4	reduce EDO DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. leadoff cycle from 6T to 5T
 3	delay DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. data latch by 1/2 clock
 2	(AMD-640) reserved
	(VT82C580VPX) Pin88 function (0 = DB32, 1 = TA9)
 1	reserved (0)
 0	delay DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. read cycle by 1T whenever write buffer contains data
	must be set if read-around-write is enabled (see #00987)
SeeAlso: #00983,#00997,#00982


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Control Register 2:
Bit(s)	Description	(Table 00997)
 7	enable EDO test mode
	when set, EDO RAM(Random Access Memory)	See also DRAM, SRAM. contents will read correctly, FPM not
 6	reserved (0)
 5-3	(AMD-640) reserved (0)
 5	(VT82C580VPX) SDRAM CASsee Communicating Applications Specification# latency (0 = latency 2, 1 = latency 3)
 4	(VT82C580VPX) reserved (0)
 3	(VT82C580VPX) enable Turbo EDO mode (0 = x-2-2-2, 1 = x-1-1-1 bursts)
 2	add one wait state for memory data-to-host data pop
 1	reduce RAS# precharge by 1T for SDRAM
 0	reduce RAS# to CASsee Communicating Applications Specification# delay for SDRAM
Note:	bits 1 and 0 have no effect unless SDRAM has been selected via the
	  DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. type register (see #00991)
SeeAlso: #00983,#00996,#00982


Bitfields for AMD-640 32-bit DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Width Control register:
Bit(s)	Description	(Table 00998)
 7	RAS# to Column Address delay (0 = 1T, 1 = 2T)
 6	delay NA# by 1T
 5-0	widths of banks 5 - 0
	AMD-640 documentation clains that all bits should be cleared
	for VT82C580VPX, settings are 0 = 64-bit, 1 = 32-bit (only applicable
	  when two banks of PBSRAM are installed)
SeeAlso: #00983,#00982,#00997,#00999


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. RefreshThe process of periodically rewriting the contents of a DRAM memory chip to keep it from fading.  The term "refresh" is also commonly applied to redrawing the image on a CRT's phosphors.   See also DRAM. Control register:
Bit(s)	Description	(Table 00999)
 7	enable CASsee Communicating Applications Specification#-before-RAS# refresh
 6	enable burst refresh (four rows every 60 us, not one every 15 us)
 5-0	reserved (0)
SeeAlso: #00983,#00998


Bitfields for AMD-640 SDRAM Control Register:
Bit(s)	Description	(Table 01000)
 7	enable 4-bank interleave for 64-Mbit SDRAMs (when bit 5 set)
 6	enable SDRAM burst write
 5	enable SDRAM bank interleave
	(when set, reduces 3-line burst from 8-1-1-1-3-1-1-1-3-1-1-1 to 8-1...)
 4	reserved (0)
 3	SDRAM CASsee Communicating Applications Specification# latency (0 = latency 2, 1 = latency 3)
 2-0	SDRAM Operation Mode
	000 normal SDRAM
	001 enable NOP command
	010 convert CPU-to-DRAM cycles into All Banks Precharge command
	011 convert CPU-to-DRAM cycles into commands on MA[11:0]
	100 enable CASsee Communicating Applications Specification#-before-RAS# cycles
	other reserved
SeeAlso: #00983,#00999


Bitfields for AMD-640 DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. Drive Strength Control register:
Bit(s)	Description	(Table 01001)
 7	bank decoding test (1="for production test only. DO NOT SET.")
 6	strength of MA[1:0] drive (0 = 12ma, 1 = 24ma)
 5	function of N17 and M17 pins
	0 N17 is RAS5#, M17 is RAS4#
	1 N17 is MA1, M17 is MA0
 4	force SMM(System Management Mode) A special CPU mode typically invoked on changes in power-supply status.  In this mode, additional hidden memory becomes available for storing the CPU's state and a control program to deal with the needs of power management or other critical events. mode (when set, act as if SMIACT# is asserted)
 3	strength of SDRAM command lines (0 = 12ma, 1 = 24ma)
 2	strength of MA[13:2] and WEx# drive (0 = 12ma, 1 = 24ma)
 1	strength of CASsee Communicating Applications Specification# drive (0 = 12ma, 1 = 24ma)
 0	strength of RAS# drive (0 = 12ma, 1 = 24ma)
SeeAlso: #00983,#00999


Bitfields for AMD-640 ECC Control Register:
Bit(s)	Description	(Table 01002)
 7	ECC mode select (0 = parity, 1 = ECC)
 6	reserved (0)
 5	assert SERR# for ECC multibit errors
 4	assert SERR# for ECC single-bit errors
 3	add 1T for SDRAM read cycles with ECC (required when ECC mode enabled)
 2	enable ECC for banks 5 and 4
 1	enable ECC for banks 3 and 2
 0	enable ECC for banks 1 and 0
SeeAlso: #00983,#01003


Bitfields for AMD-640 ECC Status Register:
Bit(s)	Description	(Table 01003)
 7	multi-bit error detected (write-clear)
 6-4	number of DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. bank containing multi-bit error (write-clear)
 3	single-bit error detected (write-clear)
 2-0	number of DRAM(Dynamic Random Access Memory) RAM memory which essentially consists of a tiny capacitor for each bit of memory.  Since capacitors do not hold a charge indefinitely, DRAM must be constantly refreshed to avoid losing its contents.  Also, the process of reading the contents of the memory are destructive, meaning extra time must be spent restoring the contents of memory addresses which are accessed, so DRAM is slower than SRAM.  See also Refresh, SRAM. bank containing single-bit error (write-clear)
SeeAlso: #00983,#01002


Bitfields for AMD-640 PCI Buffer Control register:
Bit(s)	Description	(Table 01004)
 7	enable CPU-to-PCI posted writes
 6	enable PCI-to-DRAM posted writes
 5	enable PCI-to-DRAM prefetch
 4-2	reserved (0)
 1	disable PCI retry for processor QuadWord access
 0	CPU-to-PCI buffer flushing
	0 flushing has priority over bus grants
	1 bus-grant to another PCI initiator has priority over flushing
SeeAlso: #00983


Bitfields for AMD-640 CPU-to-PCI Flow Control 1 register:
Bit(s)	Description	(Table 01005)
 7,3	PCI burst control
	00 no bursts, every write goes to write buffer
	01 burst writes placed in write buffer, non-burst writes sent to PCI
	      bus immediately after write buffers flushed
	1x all writes go to write buffer; bursting performed for burstable
	      transactions
 6	enable byte merge
 5	reserved (1)
 4	enable posted PCI I/O cycle writes
 2	eanble fast back-to-back PCI writes
 1	enable quick frame generation (FRAME# asserted one clock early)
 0	add one wait state to IRDY#
SeeAlso: #00983,#01006


Bitfields for AMD-640 CPU-to-PCI Flow Control 2 register:
Bit(s)	Description	(Table 01006)
 7	unsuccessful retry (16 or 64 times) has occurred (write-clear)
 6	retry timeout action
	0 retry continuously, recording status
	1 flush buffer; if reading, return FFFFFFFFh
 5-4	retry count and backoff
	00 retry twice, backoff processor
	01 retry 16 times, set bit 7 on failure
	10 retry four times, backoff processor
	11 retry 64 times, set bit 7 on failure
 3	discard failed data from write buffer when retry fails
 2	backoff processor if PCI read retry fails
 1	assert FRAME# one cycle earlier than indicated by offset 71h bit 1
 0	reduce TRDY#-to-BRDY# by one HCLK on processor reads of PCI target
SeeAlso: #00983,#01005,#01007


Bitfields for AMD-640 PCI Target Control register:
Bit(s)	Description	(Table 01007)
 7	slow memory decoding (must be set if fast back-to-back cycles enabled)
 6	add one wait state to TRDY# response on reads
 5	add one wait state to TRDY# response on writes
 4	reserved (0)
 3	assert STOP# after write timeout
 2	assert STOP# after read timeout
 1	enable sampling of PCI LOCK# pin
 0	force AMD-640 to initiate PCI arbitration if FRAM# not asserted within
	  16 PCI clocks of last GNT#
SeeAlso: #00983,#01006,#01008


Bitfields for AMD-640 PCI Initiator Control register:
Bit(s)	Description	(Table 01008)
 7	enable enhanced PCI commands (Memory Read Line, Memory Read Multiple,
	  and Memory Write and Invalidate)
 6	enable single-write byte merging
 5-0	reserved (0)
SeeAlso: #00983,#01007,#01008


Bitfields for AMD-640 PCI Arbitration Control 1 register:
Bit(s)	Description	(Table 01009)
 7	arbitration priority
	0 = fixed (high-to-low is REQ1#, REQ2#, REQ3#, REQ4#, PREQ#, and CPU(Central Processing Unit) The microprocessor which executes programs on your computer.)
	1 = fair (round-robin) arbitration
 6	arbitration mode
	0 arbitrate at end of REQ#
	1 arbitrate at end of each FRAME# (allows pre-emption by a
	  higher-priority initiator)
 5-4	reserved (0)
 3-0	number of idle time periods of 32 PCI clocks before arbitration is
	  forced (0000 disables timeout)
SeeAlso: #00983,#01008,#01010


Bitfields for AMD-640 PCI Arbitration Control 2 register:
Bit(s)	Description	(Table 01010)
 7	enable initiator priority rotation
	=0 use arbitration priority as set by offset 75h bit 7 (see #01009)
 6	reserved (0)
 5-4	initiator priority rotation control
	00 disabled (use offset 75h bit 7 setting)
	01 grant to processor after every PCI initiator grant
	10 grant to processor after every other PCI initiator grant
	11 grant to processor after every three PCI initiator grants
 3-0	reserved (0)
SeeAlso: #00983,#01009


Format of AMD-645 Peripheral Bus Controller, function 0 (PCI-ISA bridge) data:
Offset	Size	Description	(Table 01011)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 1106h, device ID 0586h)
 40h	BYTE	ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. bus control (see #01012)
 41h	BYTE	ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Test Mode (see #01013)
 42h	BYTE	ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. clock control (see #01014)
 43h	BYTE	ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. Decode Control (see #01015)
 44h	BYTE	keyboard controller control (see #01016)
 45h	BYTE	Type F DMAsee Direct Memory Access control (see #01017)
 46h	BYTE	Miscellaneous control 1 (see #01018)
 47h	BYTE	Miscellaneous control 2 (see #01019)
 48h	BYTE	Miscellaneous control 3 (see #01020)
 49h	BYTE	reserved
 4Ah	BYTE	IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. interrupt routing (see #01021)
 4Bh	BYTE	reserved
 4Ch	BYTE	PCI memory hole bottom, bits 23-16
 4Dh	BYTE	PCI memory hole top, bits 23-16
		(if top is <= bottom, hole is disabled)
 4Eh	WORD	DMAsee Direct Memory Access/Master memory access control 3 (see #01022)
 50h	BYTE	PnP DRQ Routing (see #01023)
 51h  3	BYTEs	reserved
 54h	BYTE	PCI IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. Edge/Level selection (see #01024)
 55h	BYTE	PnP Routing for external MIRQ0/1 (see #01025)
 56h	BYTE	PnP Routing for PCI INTB/INTA (see #01027)
 57h	BYTE	PnP Routing for PCI INTD/INTC (see #01028)
 58h	BYTE	PnP Routing for external MIRQ2 (see #01029)
 59h	BYTE	MIRQ pin configuration (see #01030)
 5Ah	BYTE	XD Power-On Strap Options (see #01031)
 5Bh	BYTE	internal RTCsee Real-Time Clock test mode (see #01032)
 5Ch  4 BYTEs	reserved
 60h	WORD	distributed DMAsee Direct Memory Access, channel 0 base address/enable (see #01033)
 62h	WORD	distributed DMAsee Direct Memory Access, channel 1 base address/enable (see #01033)
 64h	WORD	distributed DMAsee Direct Memory Access, channel 2 base address/enable (see #01033)
 66h	WORD	distributed DMAsee Direct Memory Access, channel 3 base address/enable (see #01033)
 68h	WORD	reserved
 6Ah	WORD	distributed DMAsee Direct Memory Access, channel 5 base address/enable (see #01033)
 6Ch	WORD	distributed DMAsee Direct Memory Access, channel 6 base address/enable (see #01033)
 6Eh	WORD	distributed DMAsee Direct Memory Access, channel 7 base address/enable (see #01033)
 70h 144 BYTEs	reserved
SeeAlso: #00817,#00983,#01034,#01046


Bitfields for AMD-645 ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Bus Control register:
Bit(s)	Description	(Table 01012)
 7	extra delay on ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. commands (default is disabled)
 6	enable extended ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. bus ready (default is disabled)
 5	ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. slave wait states (0=4 wait states [default], 1=5 wait states)
 4	chipset I/O wait states (0=2 wait states [default], 1=4 wait states)
 3	I/O recovery time enabled
 2	enable extended ALE
 1	no ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. wait states (default is clear, 1 wait state)
 0	enable ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. writes
SeeAlso: #01011


Bitfields for AMD-645 ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Test Mode register:
Bit(s)	Description	(Table 01013)
 7-6	reserved (0)
 5	enable fast reset via PORTIBM PC Portable (uses same BIOS as XT) 0092h
 4	reserved (0)
 3	double DMAsee Direct Memory Access clock (=0 DMAsee Direct Memory Access at 1/2 ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. clock, =1 DMAsee Direct Memory Access at full ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. clock)
 2-0	reserved (0)
SeeAlso: #01011,#01012,#01014


Bitfields for AMD-645 ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Clock Control register:
Bit(s)	Description	(Table 01014)
 7	disable "Latch IO16#"
 6-4	reserved (0)
 3	enable ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Bus clock select via bits 2-0 (=0 use PCLK/4)
 2-0	ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Bus clock select
	000 PCLK/3 (default)
	001 PCLK/2
	010 PCLK/4
	011 PCLK/6
	100 PCLK/5
	101 PCLK/10
	110 PCLK/12
	111 OSC/2
Note:	in order to safely change the ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. clock, bit 3 must first be cleared,
	  then bits 2-0 may be changed, and finally bit 3 can be set again
SeeAlso: #01011,#01013


Bitfields for AMD-645 ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. Decode Control register:
Bit(s)	Description	(Table 01015)
 7	enable 64K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at FFFE00000h-FFFEFFFFh
 6	enable 384K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at FFF80000h-FFFDFFFFh
 5	enable 32K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at E8000h-EFFFFh
 4	enable 32K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at E0000h-E7FFFh
 3	enable 32K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at D8000h-D8FFFh
 2	enable 32K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at D0000h-D7FFFh
 1	enable 32K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at C8000h-CFFFFh
 0	enable 32K ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. at C0000h-C7FFFh
SeeAlso: #01011


Bitfields for AMD-645 Keyboard Controller Control register:
Bit(s)	Description	(Table 01016)
 7-4	reserved (0)
 3	enable Mouse Lock
 2-0	reserved (0)
SeeAlso: #01011


Bitfields for AMD-645 Type-F DMAsee Direct Memory Access Control register:
Bit(s)	Description	(Table 01017)
 7	enable line buffer from ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Master/DMAsee Direct Memory Access to PCI
 6-4	enable Type F timing on DMAsee Direct Memory Access Channels 7, 6, 5
 3-0	enable Type F timing on DMAsee Direct Memory Access Channels 3-0
SeeAlso: #01011


Bitfields for AMD-645 Miscellaneous Control 1 register:
Bit(s)	Description	(Table 01018)
 7-5	reserved (0)
 4	enable command register test mode
	(when set, PCI offset 04h bits 0-1 become writable and bit 3 read-only)
 3-2	reserved (0)
 1	disallow interruptions of PCI burst reads
 0	enable posted memory writes
SeeAlso: #01011,#01019,#01020


Bitfields for AMD-645 Miscellaneous Control 2 register:
Bit(s)	Description	(Table 01019)
 7	use INIT as CPU(Central Processing Unit) The microprocessor which executes programs on your computer. reset signal instead of CPURST
 6	enable PCI transaction delay
 5	enable ports 04D0h-04D1h (per EISA(Enhanced Industry-Standard Architecture) A 32-bit superset of the IBMInternational Busiuness Machines ATIBM PC AT's expansion bus (which is now known as the ISA or Industry-Standard Architecture bus). spec)
 4	enable interrupt controller shadow register
 3	reserved (0)
 2	enable write delay transaction time-out timer
 1	enable read delay transaction time-out timer
 0	software PCI reset -- set to cause a PCI reset via PCIRST pin
SeeAlso: #01011,#01018,#01020,PORTIBM PC Portable (uses same BIOS as XT) 04D0h


Bitfields for AMD-645 Miscellaneous Control 3 register:
Bit(s)	Description	(Table 01020)
 7-4	reserved (0)
 3	disable RTCsee Real-Time Clock PORTIBM PC Portable (uses same BIOS as XT) 0074h and PORTIBM PC Portable (uses same BIOS as XT) 0075h
 2	disable integrated USBsee Universal Serial Bus controller
 1	disable integrated IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. controller
 0	add 512K to offset 4Eh bits 15-12 at top of PCI memory
SeeAlso: #01011,#01018,#01019,PORTIBM PC Portable (uses same BIOS as XT) 0074h"AMD-645"


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Interrupt Routing register:
Bit(s)	Description	(Table 01021)
 7	wait for PGNT before Grant to ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. Master/DMAsee Direct Memory Access
 6	port 00xxh bus select (0=access via SD bus, 1=access via XD bus)
 5-4	reserved (0)
 3-2	secondary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. channel IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. (same encoding as primary)
 1-0	primary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. channel IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated.
	00 IRQ14 (default for primary)
	01 IRQ15 (default for secondary)
	10 IRQ10
	11 IRQ11
SeeAlso: #01011


Bitfields for AMD-645 DMAsee Direct Memory Access/Master Memory Access Control 3 register:
Bit(s)	Description	(Table 01022)
 15-12	top of PCI memory for ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA. DMAsee Direct Memory Access/Master access, bits 23-20, less 1
 11	accesses to E0000h-EFFFFh forwarded to PCI
 10	accesses to A0000h-BFFFFh forwarded to PCI
 9	accesses to 80000h-9FFFFh forwarded to PCI
 8	accesses to 00000h-7FFFFh forwarded to PCI
 7	accesses to DC000h-DFFFFh forwarded to PCI
 6	accesses to D8000h-DBFFFh forwarded to PCI
 5	accesses to D4000h-D7FFFh forwarded to PCI
 4	accesses to D0000h-D3FFFh forwarded to PCI
 3	accesses to CC000h-CFFFFh forwarded to PCI
 2	accesses to C8000h-CBFFFh forwarded to PCI
 1	accesses to C4000h-C7FFFh forwarded to PCI
 0	accesses to C0000h-C3FFFh forwarded to PCI
SeeAlso: #01011


Bitfields for AMD-645 PnP DRQ Routing register:
Bit(s)	Description	(Table 01023)
 7-0	reserved (always read 04h)
SeeAlso: #01011,#01024


Bitfields for AMD-645 PCI IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. Edge/Level Select register:
Bit(s)	Description	(Table 01024)
 7-4	reserved
 3	PIRQA# is edge-sensitive rather than level-sensitive
 2	PIRQB# is edge-sensitive
 1	PIRQC# is edge-sensitive
 0	PIRQD# is edge-sensitive
SeeAlso: #01011,#01023,#01025


Bitfields for AMD-645 PnP IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. Routing 1 register:
Bit(s)	Description	(Table 01025)
 7-4	routing for MIRQ1 (see #01026)
 3-0	routing for MIRQ0 (see #01026)
SeeAlso: #01011,#01024


(Table 01026)
Values for AMD-645 IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. routing:
 0000	disabled
 0001	IRQ1
 0010	reserved
 0011	IRQ3
 ...
 0111	IRQ7
 1000	reserved
 1001	IRQ9
 ...
 1100	IRQ12
 1101	reserved
 1110	IRQ14
 1111	IRQ15
SeeAlso: #01025,#01027,#01028,#01029


Bitfields for AMD-645 PnP IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. Routing 2 register:
Bit(s)	Description	(Table 01027)
 7-4	routing for PIRQB# (see #01026)
 3-0	routing for PIRQA# (see #01026)
SeeAlso: #01025,#01028,#01029


Bitfields for AMD-645 PnP IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. Routing 3 register:
Bit(s)	Description	(Table 01028)
 7-4	routing for PIRQD# (see #01026)
 3-0	routing for PIRQC# (see #01026)
SeeAlso: #01025,#01027,#01029


Bitfields for AMD-645 PnP IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. Routing 4 register:
Bit(s)	Description	(Table 01029)
 7-4	reserved
 3-0	routing for MIRQ2# (see #01026)
SeeAlso: #01025,#01027,#01028


Bitfields for AMD-645 MIRQ Pin Configuration register:
Bit(s)	Description	(Table 01030)
 7-3	reserved (0)
 2	select MASTER# instead of MIRQ2
 1	select KEYLOCK instead of MIRQ1
 0	select APICCS# instead of MIRQ0
SeeAlso: #01011,#01029


Bitfields for AMD-645 XD Power-Up Strap Options register:
Bit(s)	Description	(Table 01031)
 7-4	Keyboard RP16-RP13
 3	reserved (0)
 2	enable internal RTCsee Real-Time Clock
 1	enable internal PS/2IBM PS/2, any model mouse
 0	enable internal keyboard controller
Note:	the default value of this register is latched from external pins at
	  power-up
SeeAlso: #01011


Bitfields for AMD-645 Internal RTCsee Real-Time Clock Test Mode register:
Bit(s)	Description	(Table 01032)
 7-2	reserved (0)
 1	enable access to internal RTCsee Real-Time Clock's RAM(Random Access Memory)	See also DRAM, SRAM. when RTCsee Real-Time Clock is disabled
	  (see PORTIBM PC Portable (uses same BIOS as XT) 0074h"AMD-645")
 0	reserved (0)
SeeAlso: #01011


Bitfields for AMD-645 Distributed DMAsee Direct Memory Access Base/Enable register:
Bit(s)	Description	(Table 01033)
 15-4	base address bits 15-4 for Channel N
 3	enable DMAsee Direct Memory Access channel
 2-0	reserved (0)
SeeAlso: #01011


Format of AMD-645 Peripheral Bus Controller, function 1 (IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Control) data:
Offset	Size	Description	(Table 01034)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 1106h [VIA Technologies], device ID 0571h)
 09h	BYTE	programming interface
		bit 7: Master IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. capability
		bits 6-4: reserved (0)
		bit 3: secondary channel supports operating mode selection
		bit 2: use native PCI mode, not compatibility mode for sec. ch.
		bit 1: primary channel supports operating mode selection
		bit 0: use native PCI mode, not compatibility mode for pri. ch.
 10h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	primary data/command base address
 14h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	primary control/status base address
 18h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	secondary data/command base address
 1Ch	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	secondary control/status base address
 20h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	bus master control base address (default 0000CC01h)
 40h	BYTE	chip enable (see #01035)
 41h	BYTE	IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. configuration (see #01036)
 42h	BYTE	reserved ("do not program")
 43h	BYTE	FIFO configuration (see #01037)
 44h	BYTE	miscellaneous control 1 (see #01038)
 45h	BYTE	miscellaneous control 2 (see #01039)
 46h	BYTE	miscellaneous control 3 (see #01040)
 47h	BYTE	unused???
 48h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	drive timing control (see #01041)
 4Ch	BYTE	address setup time (see #01042)
 4Dh	BYTE	reserved ("do not program")
 4Eh	BYTE	secondary non-01F0h port access timing (see #01043)
 4Fh	BYTE	primary non-01F0h port access timing (see #01043)
 50h	BYTE	UltraDMA/33 extended timing control, Sec. Drive 1 (see #01044)
 51h	BYTE	UltraDMA/33 extended timing control, Sec. Drive 0 (see #01044)
 52h	BYTE	UltraDMA/33 extended timing control, Pri. Drive 1 (see #01044)
 53h	BYTE	UltraDMA/33 extended timing control, Pri. Drive 0 (see #01044)
 54h  4 BYTEs	reserved
 58h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	"reserved"
		(appears to be an additional set of drive timing controls)
 5Ch  4 BYTEs	???
 60h	WORD	primary sector size (see #01045)
 62h  6 BYTEs	reserved
 68h	WORD	secondary sector size (see #01045)
 6Ah 150 BYTEs	reserved
Note:	the AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. controller is compatible with the SFF 8038i v1.0 spec
SeeAlso: #00817,#01011,#01046


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Chip Enable register:
Bit(s)	Description	(Table 01035)
 7-2	reserved (00001)
 1	enable primary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. channel
 0	enable secondary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. channel
SeeAlso: #01034,#01036


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Configuration register :
Bit(s)	Description	(Table 01036)
 7	enable primary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. read-prefetch buffer
 6	enable primary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. post write buffer
 5	enable secondary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. read-prefetch buffer
 4	enable secondary IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. post write buffer
 3-0	reserved (0110)
SeeAlso: #01034,#01035,3813


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. FIFO Configuration register:
Bit(s)	Description	(Table 01037)
 7	reserved (0)
 6-5	FIFO configuration
	00	primary channel = 16, secondary channel = 0
	01/10	primary channel = 8, secondary channel = 8
	11	primary channel = 0, secondary channel = 16
 4	reserved (1)
 3-2	primary channel FIFO threshold
	00 = completely full
	01 = 3/4 full
	10 = 1/2 full
	11 = 1/4 full
 1-0	secondary channel FIFO threshold (same settings as bits 3-2)
SeeAlso: #01034,#01036


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Miscellaneous Control 1 register:
Bit(s)	Description	(Table 01038)
 7	reserved (0)
 6	number of wait states on Master Read Cycle IRDY#
 5	number of wait states on Master Write Cycle IRDY#
 4	enable 1/2 clock advance on FIFO output
 3	enable bus-master IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. status register read retry
 2-0	reserved (0)
SeeAlso: #01034,#01039,#01040


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Miscellaneous Control 2 register:
Bit(s)	Description	(Table 01039)
 7	reserved (0)
 6	swap interrupts between the two IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. channels
 5-0	reserved (0)
SeeAlso: #01034,#01038,#01040


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Miscellaneous Control 3 register:
Bit(s)	Description	(Table 01040)
 7	enable FIFO flush for read DMAsee Direct Memory Access on primary channel interrupt
 6	enable FIFO flush for read DMAsee Direct Memory Access on secondary channel interrupt
 5	enable FIFO flush for each sector on primary channel
 4	enable FIFO flush for each sector on secondary channel
 3-2	reserved
 1-0	maximum DRDY# pulse width
	00 unlimited
	01 64 PCI clocks
	10 128 PCI clocks
	11 192 PCI clocks
SeeAlso: #01034,#01038,#01039


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Drive Timing Control register:
Bit(s)	Description	(Table 01041)
 31-28	primary drive 0 active DIOR#/DIOW# pulse width
 27-24	primary drive 0 DIOR#/DIOW# recovery time (PCI clocks, less 1)
 23-20	primary drive 1 active pulse width (PCI clocks, less 1)
 19-16	primary drive 1 recovery time
 15-12	secondary drive 0 active pulse width
 11-8	secondary drive 0 recovery time
 7-4	secondary drive 1 active pulse width
 3-0	secondary drive 1 recover time (PCI clocks, less 1)
SeeAlso: #01034,#01042


Bitfields for AMD-645 IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself.	 See also ESDI. Address Setup Time register:
Bit(s)	Description	(Table 01042)
 7-6	primary drive 0 address setup time
	00 = 1T
	01 = 2T
	10 = 3T
	11 = 4T
 5-4	primary drive 1 address setup time (same values as above)
 3-2	secondary drive 0 address setup time
 1-0	secondary drive 1 address setup time
SeeAlso: #01034,#01041


Bitfields for AMD-645 Non-01F0h Port Access Timing register:
Bit(s)	Description	(Table 01043)
 7-4	width of DIOR#/DIOW# active pulse in PCI clocks (less 1)
 3-0	DIOR#/DIOW# recovery time in PCI clocks (less 1)
SeeAlso: #01011


Bitfields for AMD-645 UltraDMA/33 Extended Timing Control register:
Bit(s)	Description	(Table 01044)
 7	method for enabling UltraDMA mode on drive
	0 using "Set Feature" command
	1 using bit 6 of this register
 6	enable UltraDMA mode for drive
 5	UltraDMA transfer mode
	0 UltraDMA DMAsee Direct Memory Access mode
	1 UltraDMA PIO mode
 4-2	reserved (0)
 1-0	drive cycle time
	00 = 2T
	...
	11 = 5T
SeeAlso: #01011


Bitfields for AMD-645 SectorThe smallest addressable unit of data on a disk; under MS-DOS, this is normally 512 bytes.  See also Track. Size register:
Bit(s)	Description	(Table 01045)
 15-12	reserved
 11-0	sector size in bytes (default 200h)
SeeAlso: #01011


Format of AMD-645 Peripheral Bus Controller, function 2 (USBsee Universal Serial Bus Controller) data:
Offset	Size	Description	(Table 01046)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 1106h, device ID 3038h)
 20h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	base address of USBsee Universal Serial Bus I/O ports (see PORTIBM PC Portable (uses same BIOS as XT) xxxxh"AMD-645 - USBsee Universal Serial Bus"
 40h	BYTE	miscellaneous control 1 (see #01047)
 41h	BYTE	miscellaneous control 2 (see #01048)
 42h  2 BYTEs	reserved
 44h  3 BYTEs	reserved ("do not program")
 47h	BYTE	reserved
 48h 24 BYTEs	reserved
 60h	BYTE	USBsee Universal Serial Bus release number (read-only, 10h)
 61h 95 BYTEs	reserved
 C0h	WORD	USBsee Universal Serial Bus legacy support (read-only, 2000h)
 C2h 62 BYTEs	reserved
SeeAlso: #00817,#00983,#01011,#01034,#01049


Bitfields for AMD-645 USBsee Universal Serial Bus Miscellaneous Control 1 register:
Bit(s)	Description	(Table 01047)
 7	PCI memory commands
	0 support memory-read-line, memory-read-multiple, and
	  memory-write-and-invalidate
	1 memory read and memory write commands only
 6	do not disable port on EOF babble
 5	eanble PCI parity checking and PERR# generation
 4	reserved (0)
 3	USBsee Universal Serial Bus data length
	0 allow TD length up to 1280 bytes
	1 limit to 1023
 2	enable USBsee Universal Serial Bus power management
 1	DMAsee Direct Memory Access limited to 8-DW burst instead of 16-DW
 0	insert one PCI wait state
SeeAlso: #01046,#01048


Bitfields for AMD-645 USBsee Universal Serial Bus Miscellaneous Control 2 register:
Bit(s)	Description	(Table 01048)
 7-3	reserved (0)
 2	only trap port 60h/64h bits when trap-enable bits are set
 1	do not pass A20GATE command sequence (from UHCI) through I/O port 64h
 0	reserved (0)
SeeAlso: #01046,#01047,PORTIBM PC Portable (uses same BIOS as XT) 0064h


Format of AMD-645 Peripheral Bus Controller, function 3 (Power Mgmt) data:
Offset	Size	Description	(Table 01049)
 00h 64 BYTEs	header (see #00878)
		(vendor ID 1106h, device ID 3040h)
 20h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	base address for I/O ports (see PORTIBM PC Portable (uses same BIOS as XT) xxxxh"AMD-645")
 40h	BYTE	pin configuration (see #01050)
 41h	BYTE	general configuration (see #01051)
 42h	BYTE	SCI interrupt configuration (see #01052)
 43h	BYTE	reserved
 44h	WORD	primary interrupt channel
		bit 2 is reserved; setting any other bit N makes IRQN the
		  primary interrupt channel
 46h	WORD	secondary interrupt channel
		bit 2 is reserved; setting any other bit N makes IRQN the
		  secondary interrupt channel
 48h  8 BYTEs	unused???
 50h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	GP timer control (see #01053)
 54h 13	BYTEs	reserved
 61h	BYTE	programming interface read value (value to be returned by
		  configuration register 09h) (write-only)
 62h	BYTE	subclass read value (value to be returned by
		  configuration register 0Ah) (write-only)
 63h	BYTE	base class read value (value to be returned by configuration
		  register 0Bh) (write-only)
 64h 156 BYTEs	reserved
SeeAlso: #00817,#00983,#01011,#01034,#01046,#01049


Bitfields for AMD-645 PM Pin Configuration register:
Bit(s)	Description	(Table 01050)
 7	GPIO4 configuration (0 = Pin136 is GPO_WE, 1 = Pin136 is GPIO4)
 6	GPIO3 configuration (0 = Pin92 is GPI_RE#, 1 = Pin92 is GPIO3)
 5-0	reserved (0)
SeeAlso: #01049,#01051


Bitfields for AMD-645 PM General Configuration register:
Bit(s)	Description	(Table 01051)
 7	enable debounce of PWRBTN# input
 6	enable ACPI timer reset
 5-4	reserved ("do not program")
 3	select ACPI timer size (0 = 24 bits, 1 = 32 bits)
 2	enable PCI Frame Activation as Resume Event im power state C2
 1	clock-throttling cycle time
	0 = 32 usec clock, 512 usec cycle time (default)
	1 = 1 msec clock 16 msec cycle time
 0	reserved ("do not program")
SeeAlso: #01049,#01050,MEM xxxxh:xxx0h"ACPI"


Bitfields for AMD-645 PM SCI Interrupt Configuration register:
Bit(s)	Description	(Table 01052)
 7-4	reserved (0)
 3-0	interrupt assignment
	0000 disabled
	else IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated. number (except IRQ2 is reserved)
SeeAlso: #01049


Bitfields for AMD-645 PM GP Timer Control register:
Bit(s)	Description	(Table 01053)
 31-30	power-conservation mode timer
	00 = 1/16 sec
	01 = 1/8 sec
	10 = 1 sec
	11 = 1 minute
 29	(read) set when system is in power-conservation mode
 28	enable power-conservation mode
 27-26	secondary event timer
	00 = 2 msec
	01 = 64 msec
	10 = 1/2 sec
	11 = 0.25 msec after EOI(End of Interrupt) A particular command sent to the interrupt controller to indicate that the interrupt has been handled by software and that new interrupts of the same or lower priority may now be signalled by the interrupt controller.
 25	secondary event occurred, secondary event timer is counting down
 24	enable secondary event timer
 23-16	GP1 Timer count (see bits 5-4)
 15-8	GP0 Timer count (see bits 1-0)
 7	start GP1 timer
 6	automatically reload GP1 timer after counting down to 0
 5-4	time base for GP1 timer
	00 disabled
	01 = 32 microseconds
	10 = 1 second
	11 = 1 minute
 3	start GP0 timer
 2	automatically reload GP0 timer after counting down to 0
 1-0	time base for GP0 timer
	00 disabled
	01 = 1/16 second
	10 = 1 second
	11 = 1 minute
SeeAlso: #01049