PORTIBM PC Portable (uses same BIOS as XT) 03D6-03D7 - CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA. (Color Graphics Adapter) - MIRRORS OF 03D4/03D5

03D6  -W  same as 03D4
	(under OS/2, reads return 0 if full-screen DOS session,
	  nonzero if windowed DOS session)
03D7  RW  same as 03D5
                                                                                

PORTIBM PC Portable (uses same BIOS as XT) 03D6-03D7 - Chips&Technologies VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. - EXTENSION REGISTERS

03D6  -W  extension register index (see #P0762,#P0763)
03D7  RW  extension register data


(Table P0762)
Values for Chips&Technologies 64200 extension register index:
 00h	"XR00"	chip version (see #P0764)
 01h	"XR01"	configuration (see #P0765)
 02h	"XR02"	CPU(Central Processing Unit) The microprocessor which executes programs on your computer. interface control (see #P0767)
 03h	"XR03"	master control (see #P0768)
 04h	"XR04"	memory control (see #P0770)
 05h	"XR05"	clock control (see #P0771)
 06h	"XR06"	color palette control / 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. interface
 07h	"XR07"	reserved
 08h	"XR08"	general purpose output select B
 09h	"XR09"	general purpose output select A
 0Ah	"XR0A"	cursor address top
 0Bh	"XR0B"	CPU(Central Processing Unit) The microprocessor which executes programs on your computer. paging (see #P0777)
 0Ch	"XR0C"	start address top (see #P0778)
 0Dh	"XR0D"	auxiliary offset (see #P0780)
 0Eh	"XR0E"	text mode control (see #P0781)
 0Fh	"XR0F"	configuration register 2
 10h	"XR10"	single/low map register (see #P0782)
 11h	"XR11"	high map register (see #P0783)
 14h	"XR14"	emulation mode (see #P0784)
 15h	"XR15"	write protect (see #P0785)
 16h	"XR16"	trap enable
 17h	"XR17"	trap status
 18h	"XR18"	alternate horizontal display end
 19h	"XR19"	alternate horizontal sync start / half-line
 1Ah	"XR1A"	alternate horizontal sync end (see #P0789)
 1Bh	"XR1B"	alternate horizontal total
 1Ch	"XR1C"	alternate horizontal blank start / horizontal panel size
 1Dh	"XR1D"	alternate horizontal blank end (see #P0790)
 1Eh	"XR1E"	alternate offset
 1Fh	"XR1F"	virtual EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors. switch (see #P0791)
 20h	"XR20"	453 Interface ID
 21h	"XR21"	Sliding Hold A
 22h	"XR22"	Sliding Hold B
 23h	"XR23"	SHC / WBM Control
 24h	"XR24"	Flat-Panel Alternate Max Scanline / SHD / WBM Pattern
 25h	"XR25"	Flat-Panel "AltGrHVirtPanelSize" / 453 Pin Definition
 26h	"XR26"	453 Configuration
 27h	"XR27"	reserved
 28h	"XR28"	video interface (see #P0792)
 29h	"XR29"	function control
 2Ah	"XR2A"	frame interrupt count
 2Bh	"XR2B"	default video color (to be displayed when screen blanked)
 2Ch	"XR2C"	Flat-Panel VSync (FLM) Delay / force H high
 2Dh	"XR2D"	Flat-Panel HSync (LP) delay / force H low
 2Eh	"XR2E"	Flat-Panel HSync (LP) delay / force V high
 2Fh	"XR2F"	Flat-Panel HSync (LP) width / force V low
 30h	"XR30"	graphics cursor start address (high)
 31h	"XR31"	graphics cursor start address (low)
 32h	"XR32"	graphics cursor end address
 33h	"XR33"	graphics cursor X (high)
 34h	"XR34"	graphics cursor X (low)
 35h	"XR35"	graphics cursor Y (high)
 36h	"XR36"	graphics cursor Y (low)
 37h	"XR37"	graphics cursor mode
 38h	"XR38"	graphics cursor mask
 39h	"XR39"	graphics cursor color 0
 3Ah	"XR3A"	graphics cursor color 1
 3Bh	"XR3B"	reserved
 3Ch	"XR3C"	serial / row count (see #P0799)
 3Dh	"XR3D"	multiplexor mode (see #P0801)
 41h	"XR41"	virtual EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors. switch register (82C453)
 44h	"XR44"	software flag register 1
 45h	"XR45"	software flag register 2 / foreground color
 50h	"XR50"	panel format
 51h	"XR51"	display type
 52h	"XR52"	power-down control / panel size
 53h	"XR53"	line graphics override
 54h	"XR54"	flat-panel interface / alternate miscellaneous output
 55h	"XR55"	horizontal compensation / text 350_A compensation
 56h	"XR56"	horizontal centering / text 350_B compensation
 57h	"XR57"	vertical compensation / text 400 compensation
 58h	"XR58"	vertical centering / graphics 350 compensation
 59h	"XR59"	vertical line insertion / graphics 400 compensation
 5Ah	"XR5A"	vertical line replication / FP vertical display start 400
 5Bh	"XR5B"	flat-panel vertical display end 400 
 5Ch	"XR5C"	weight control clock A
 5Dh	"XR5D"	weight control clock B
 5Eh	"XR5E"	ACDCLK control
 5Fh	"XR5F"	power-down mode refresh
 60h	"XR60"	blink rate control
 61h	"XR61"	SmartMap™ control
 62h	"XR62"	SmartMap™ shift parameter
 63h	"XR63"	SmartMap™ color mapping control
 64h	"XR64"	flat-panel alternate vertical total
 65h	"XR65"	flat-panel alternate overflow
 66h	"XR66"	flat-panel alternate vertical sync start
 67h	"XR67"	flat-panel alternate vertical sync end
 68h	"XR68"	flat-panel vertical panel size / alternate vertical DE end
 69h	"XR69"	flat-panel vertical display start 350
 6Ah	"XR6A"	flat-panel vertical display end 350
 6Bh	"XR6B"	flat-panel vertical overflow 2
 6Ch	"XR6C"	weight control clock C
 6Dh	"XR6D"	FRC control
 6Eh	"XR6E"	polynomial FRC control
 6Fh	"XR6F"	frame buffer control
 70h	"XR70"	setup/disable control (see #P0807)
 71h-7Ch	reserved
 7Dh	"XR7D"	flat-panel compensation diagnostic
 7Eh	"XR7E"	CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA./Hercules color selection (see #P0815)
 7Fh	"XR7F"	diagnostics (see #P0816)
!!! chips\64200.pdf p.28, p.72
Note:	not all C&T chips support all of the above registers; see the tables
	  for the individual registers for a list of supporting chipsets
SeeAlso: #P0763


(Table P0763)
Values for Chips&Technologies 64310 extension register index:
 00h	"XR00"	chip version (see #P0764)
 01h	"XR01"	configuration (see #P0766)
 02h	"XR02"	CPU(Central Processing Unit) The microprocessor which executes programs on your computer. interface control (see #P0767)
 03h	"XR03"	CPU(Central Processing Unit) The microprocessor which executes programs on your computer. interface control 2 (see #P0769)
 04h	"XR04"	memory control (see #P0770)
 05h	"XR05"	memory control 2 (see #P0772)
 06h	"XR06"	color palette control / 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. interface (see #P0773)
 07h	"XR07"	DRxx I/O base ???
 08h	"XR08"	linear frame buffer base address low register (see #P0774)
 09h	"XR09"	linear frame buffer base address high register (see #P0775)
 0Ah	"XR0A"	XRAM mode register (see #P0776)
 0Bh	"XR0B"	CPU(Central Processing Unit) The microprocessor which executes programs on your computer. paging (see #P0777)
 0Ch	"XR0C"	start address top (see #P0779)
 0Dh	"XR0D"	auxiliary offset (see #P0780)
 0Eh	"XR0E"	text mode control (see #P0781)
 0Fh	"XR0F"	software flag register 0 (reserved for 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./driver use)
 10h	"XR10"	single/low map register (see #P0782)
 11h	"XR11"	high map register (see #P0783)
 12h-13h	reserved
 14h	"XR14"	emulation mode (see #P0784)
 15h	"XR15"	write protect (see #P0785)
 16h	"XR16"	vertical overflow register (see #P0786)
 17h	"XR17"	horizontal overflow register (see #P0787)
 18h	"XR18"	reserved
 19h	"XR19"	alternate horizontal sync start / half-line (see #P0788)
 1Ah-1Bh	reserved
 1Ch	"XR1C"	alternate horizontal blank start / horizontal panel size
 1Dh-27h	reserved
 28h	"XR28"	video interface (see #P0792)
 29h-2Ah	reserved
 2Bh	"XR2B"	software flag register 1 (used by device drivers)
 2Ch-2Fh	reserved
 30h	"XR30"	clock divide control register (see #P0793)
 31h	"XR31"	clock M-divisor register (see #P0794)
 32h	"XR32"	clock N-divisor register (see #P0795)
 33h	"XR33"	clock control register (see #P0796)
 34h-39h	reserved
 3Ah	"XR3A"	color key compare data 0 (see #P0797)
 3Bh	"XR3B"	color key compare data 1 (see #P0798)
 3Ch	"XR3C"	color key compare data 2 (see #P0800)
 3Dh	"XR3D"	color key compare mask 0 (see #P0802)
 3Eh	"XR3E"	color key compare mask 1 (see #P0803)
 3Fh	"XR3F"	color key compare mask 2 (see #P0804)
 40h	"XR40"	BitBlt config register (see #P0805)
 41h	"XR41"	reserved
 42h-43h	reserved
 44h	"XR44"	software flag register 2 (reserved for 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./driver use)
 45h	"XR45"	reserved
 46h-4Fh	reserved
 50h-51h	reserved
 52h	"XR52"	refresh control register (see #P0806)
 53h-5Fh	reserved
 60h	"XR60"	blink rate control
 61h-6Fh	reserved
 70h	"XR70"	setup/disable control (see #P0807)
 71h	"XR71"	GPIO control register (see #P0808)
 72h	"XR72"	GPIO data register (see #P0809)
 73h	"XR73"	misc control register (see #P0810)
 74h	"XR74"	configuration register 2 (see #P0811)
 75h	"XR75"	software flag register 3 (reserved for 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./driver use)
 76h-79h	reserved
 7Ah	"XR7A"	test index register (see #P0812)
 7Bh	"XR7B"	test control register (see #P0813)
 7Ch	"XR7C"	test data register (see #P0814)
 7Dh	"XR7D"	diagnostic register (reserved; should not be read or written)
 7Eh	"XR7E"	reserved
 7Fh	"XR7F"	diagnostic register (reserved; should not be read or written)
SeeAlso: #P0762


Bitfields for Chips&Technologies "XR00" chip version:
Bit(s)	Description	(Table P0764)
 7-4	chip type
	0000 = 82C451
	0001 = 82C452
	0010 = 82C455
	0011 = 82C453
	0100 = 82C450
	0101 = 82C456
	0110 = 82C457
	0111 = 65520
	1000 = 65530 / 65525
	1001 = 65510 Flat-Panel Controller
	1010 = 64200 Wingine
	1011 = 64300/301 Wingine DGX (if bit 3 clear)
	1011 = 64310 Wingine DGX-PCI (if bit 3 set)
 3-0	chip revision (0000 = first silicon)
Note:	this register is read-only
SeeAlso: #P0762,#P0765


Bitfields for Chips&Technologies 64200 "XR01" configuration:
Bit(s)	Description	(Table P0765)
 7-4	configuration bits 7-4 (latched from pins on falling edge of RESET)
 3	memory configuration
	0 video memory pins always drive
	1 video memory pins only driven when XR03 bit 0 is clear (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. mode)
 2	source of pixel clock
	0 oscillator (CLK0-CLK3 are pixel-clock inputs, which are selected by
	  MSR(Model-Specific Register) Additional, indirectly-accessible, registers containing control or status information about various aspects of the processor such as caches, performance counters, and the like.	These registers, accessible via the RDMSR and WRMSR instructions, were added with the Pentium and later-model 486 processors. bits 3-2)
	1 clock chip (CLK0 is pixel clock input, CLK1-CLK3 are CSELx outputs)
 1-0	bus type
	00 PCI
	01 Microchannel
	10 local bus
	11 ISA(Industry-Standard Architecture) The expansion bus used by the IBMInternational Busiuness Machines PCIBM PC/ATIBM PC AT.  See also EISA.
Note:	this register is read-only
SeeAlso: #P0762,#P0764,#P0767,#P0766


Bitfields for Chips&Technologies 64300/64310 "XR01" configuration:
Bit(s)	Description	(Table P0766)
 7-6	(64310) reserved (0)
 7	(64300) VL-Bus CPU(Central Processing Unit) The microprocessor which executes programs on your computer. speed???
 6	(64300) VL-Bus zero wait state???
 5	(64310) OSC source
	0 = external
	1 = internal
 4	(64310) clock source
	0 = external (82C404C)
	1 = internal
 3	(64310) chip (bus interface and RAMDAC) enable
 2	(64310) 64310 isolate
	0 = 64310 cannot be disabled
	1 = 64310 can be disabled using port 106h in setup mode
	(64310 may also be disabled using PCI configuration registers)
 1-0	(64310) bus type
	00 reserved
	01 32-bit PCI
	10 reserved
	11 32-bit local bus
SeeAlso: #P0763,#P0765


Bitfields for Chips&Technologies "XR02" CPU(Central Processing Unit) The microprocessor which executes programs on your computer. interface register:
Bit(s)	Description	(Table P0767)
 7	status of attribute flip-flop (read-only) (0 = index, 1 = data)
 6	(64200) palette address decoding
	0 access only at PORTIBM PC Portable (uses same BIOS as XT) 03C6h-03C9h
	1 also access at PORTIBM PC Portable (uses same BIOS as XT) 83C6h-83C9h (for RAMDACs with 8 registers)
	(64310) reserved (0)
 5	I/O address decoding
	0 decode all 16 bits of address
	1 only decode low ten bits of address for 3B4h,3B5h,3B8h,3BAh,3BFh,
	  3C0h-3C2h,3C4h,3C5h,3CEh,3CFh,3D4h,3D5h,3D8h-3DAh
 4-3	mapping of Attribute Controller
	00 VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. mapping - write index and data at 03C0h (8-bit only)
	01 16-bit mapping - write index at 03C0h, data at 03C1h
	10 (64200 only) EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors. mapping - write index at 03C0h, data at 03C0h or
		  03C1h (8-bit)
	11 reserved
 2-0	reserved (0)
SeeAlso: #P0762,#P0765,PORTIBM PC Portable (uses same BIOS as XT) 83C6h


Bitfields for Chips&Technologies "XR03" Master Control register:
Bit(s)	Description	(Table P0768)
 7	XREQ# direction (=0 input, =1 output)
 6	XREQ# divide (=0 DispEnable for all lines, =1 even-numbered lines)
 5	XREQ# mode (=0 DispEnable only, =1 split-buffer VRAM transfer timing)
	(see "XR3C"">#P0799"XR3C","XR3D"">#P0801"XR3D")
 4	alternate VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. address
	=1 map at PORTIBM PC Portable (uses same BIOS as XT) 02C6h-02C9h instead of 03C6h-03C9h
 3-2	reserved
 1	alternate palette address
	=1 map at PORTIBM PC Portable (uses same BIOS as XT) 02Bxh or PORTIBM PC Portable (uses same BIOS as XT) 02Dxh instead of 03Bxh/03Dxh
 0	Wingine/VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. select
	=0 VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.
	=1 Wingine (memory pins are tri-stated)
Note:	a write-only copy of this register may be accessed at PORTIBM PC Portable (uses same BIOS as XT) 0022h
	  (index E0h) and PORTIBM PC Portable (uses same BIOS as XT) 0023h; a read-write copy exists in systems with
	  built-in Wingine support
SeeAlso: #P0762,#P0767,#P0770,#P0769


Bitfields for Chips&Technologies 64310 "XR03" CPU(Central Processing Unit) The microprocessor which executes programs on your computer. interface register 2:
Bit(s)	Description	(Table P0769)
 7-2	reserved (0)
 1	DRxx register access enable (I/O port defined in XR07 ???)
 0	palette write shadow
SeeAlso: #P0763,#P0768


Bitfields for Chips&Technologies "XR04" Memory Control register:
Bit(s)	Description	(Table P0770)
 7-6	(64200) reserved (0)
 7	(64310) FIFO depth
	0 = bus FIFO is 8 deep
	1 = bus FIFO is 4 deep
 6	(64310) PCI burst enable
 5	(64200) enable CPU(Central Processing Unit) The microprocessor which executes programs on your computer. memory write buffer
	(64310) CPU(Central Processing Unit) The microprocessor which executes programs on your computer. bus FIFO enable
 4-3	reserved (0)
 2	memory wraparound
	=1 enable bit 17 of CRTC address counter
 1-0	(64310) memory configuration
	   data path  chips   config   total
	00    16-bit	  4  256Kx4   1/2 MB
			  1  256Kx16  1/2 MB
	01    32-bit	  8  256Kx4	1 MB
			  2  256Kx16	1 MB
	10    32-bit	 16  256Kx4	2 MB
			  4  256Kx16	2 MB
	11  reserved
 1	(64200) reserved (0)
 0	(64200) memory configuration
	=0 8-bit data, two 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. chips of 256Kx4
	=1 16-bit data, four 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. chips of 256Kx4
SeeAlso: #P0762,#P0768,#P0763


Bitfields for Chips&Technologies "XR05" Clock Control register:
Bit(s)	Description	(Table P0771)
 !!!
SeeAlso: #P0762


Bitfields for Chips&Technologies 64310 "XR05" Memory Control register 2:
Bit(s)	Description	(Table P0772)
 7	VAFC PCLK/2
	0 = DCLK=PCLK
	1 = DCLK=PCLK/2
 6	VAFC enable (XR71 bits 5, 3 and 2 must be 0)
 5	reserved (0)
 4	256Kx16 access format
	0 = 2 CASsee Communicating Applications Specification / 1 WE
	1 = 2 WE / 1 CASsee Communicating Applications Specification
 3-0	reserved
SeeAlso: #P0763


Bitfields for Chips&Technologies "XR06" color palette control / 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. interface:
Bit(s)	Description	(Table P0773)
 7-5	(64310) reserved (0)
 4	(64310) video overlay on color key enable
 3-2	(64310) display mode color depth
	00 = 4BPP / 8BPP
	01 = 15BPP (5-5-5) Sierra compatible
	10 = 24BPP
	11 = 16BPP (5-6-5) XGA(Extended Graphics Array) compatible
 1	(64310) internal DAC(Digital-to-Analog Converter) A hardware device (in its simplest form, nothing more than a set of interconnected resistors) which converts a digital number into an analog signal whose voltage is proportional to the value of the digital number.  VGAVideo Graphics Array and later color video boards use DACs to convert color values into the analog signals sent to the display; sound boards normally use DACs as well. disable
 0	(64310) enable external pixel data
	0 = VID15-0 and KEY inputs for live video overlay
	1 = P7-0 and BLANK# outputs for external feature connector/external
	  color keying (XR73 bit 5 must be set)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR08" linear frame buffer base low:
Bit(s)	Description	(Table P0774)
 7-6	linear frame buffer base address low (VL-Bus only)
	(bits 23-22 of linear frame buffer base address)
	(LFB is 4 MB boundary within 4 GB address space. Upper 2 MB is used
	  for memory mapped I/O.)
 5-0	reserved (0)
SeeAlso: #P0763,#P0775


Bitfields for Chips&Technologies 64310 "XR09" linear frame buffer base high:
Bit(s)	Description	(Table P0775)
 7-0	linear frame buffer base address high (VL-Bus only)
	(bits 23-22 of linear frame buffer base address)
	(LFB is 4 MB boundary within 4 GB address space. Upper 2 MB is used
	  for memory mapped I/O.)
SeeAlso: #P0763,#P0774


Bitfields for Chips&Technologies 64310 "XR0A" XRAM mode register:
Bit(s)	Description	(Table P0776)
 7	reserved (0)
 6	disable upper XRAM in 2MB modes
	0 = upper XRAM not enabled
	1 = upper XRAM enabled
	(used in systems with 2MB frame buffer but only single 256Kx4 XRAM)
 5	XRAM diagnostic 64 (0)
 4	synchronous XRAM enable
 3	asynchronous XRAM enable
 2-1	BitBlt update
	00 = no update during BitBlt
	11 = BitBlt update enabled
 0	XRAM test enable
	0 = XRAM normal mode
	1 = XRAM read/write
SeeAlso: #P0763


Bitfields for Chips&Technologies "XR0B" CPU(Central Processing Unit) The microprocessor which executes programs on your computer. Paging register:
Bit(s)	Description	(Table P0777)
 7-3	(64200) reserved (0)
 7	(64310) big-endian byte swap (32 bpp swap)
	0 = no swap
	1 = swap bytes 0-3 and 1-2
 6	(64310) big-endian byte swap (16 bpp swap)
	0 = no swap
	1 = swap bytes 0-1 and 2-3
 4	(64310) linear addressing enable
 3	(64310) reserved (0)
 2	divide CPU(Central Processing Unit) The microprocessor which executes programs on your computer. addresses by 4 (chain-4 mode)
 1	use two maps for CPU(Central Processing Unit) The microprocessor which executes programs on your computer. to access extended video memory (see #P0782,#P0783)
 0	memory-mapping mode
	=0 VGA-compatible
	=1 extended mapping for >= 512K video memory
SeeAlso: #P0762,#P0778,#P0763


Bitfields for Chips&Technologies 64200 "XR0C" Start Address Top register:
Bit(s)	Description	(Table P0778)
 7-1	reserved (0)
 0	high-order bit of display start address when 512K display memory used
SeeAlso: #P0762,#P0777,#P0779


Bitfields for Chips&Technologies 64310 "XR0C" Start Address Top register:
Bit(s)	Description	(Table P0779)
 7	reserved
 6	high map bit 8
 4	low map bit 8
 3-0	high-order bits of display start address
SeeAlso: #P0763,#P0778


Bitfields for Chips&Technologies "XR0D" Auxiliary Offset register:
Bit(s)	Description	(Table P0780)
 7-3	reserved (0)
 2	(64200) reserved (0)
	(64310) msb of row offset register (CRT controller register 13h)
 1-0	(64310) reserved (0)
 1	(64200) LSB of memory offset (CR13) in Chain and Chain-4 modes
 0	(64200) LSB of alternate memory offset (XR1E) in Chain/Chain-4 modes
SeeAlso: #P0762


Bitfields for Chips&Technologies "XR0E" Text Mode Control register:
Bit(s)	Description	(Table P0781)
 7-4	reserved (0)
 3	cursor style (0 = replace, 1 = XOR)
 2	disable cursor blink
 1	reserved (0)
 0	(64200) reserved (0)
	(64310) extended text mode font scrambling in plane 2 enable
SeeAlso: #P0762,#P0763


Bitfields for Chips&Technologies "XR10" Single/Low Map register:
Bit(s)	Description	(Table P0782)
 7-0	(64310) single/low map base address bits 17-10
	(single map mode base address if XR0B bit 1 = 0, dual map mode lower
	  map base address if XR0B bit 1 = 1)
!!!chips\64200.pdf p.80
SeeAlso: #P0762,#P0783,#P0763


Bitfields for Chips&Technologies "XR11" High Map register:
Bit(s)	Description	(Table P0783)
 7-0	(64310) dual map mode high map base address bits 17-10
	  (if XR0B bit 1 = 1)
SeeAlso: #P0762,#P0782


Bitfields for Chips&Technologies "XR14" Emulation Mode register:
Bit(s)	Description	(Table P0784)
 7	enable interrupt output function (=0 tri-state IRQ(Interrupt ReQuest) A hardware line connected to the interrupt controller chip which signals that a CPU interrupt should be generated.# line)
 6	(64200) enable VSync status bit at PORTIBM PC Portable (uses same BIOS as XT) 03BAh/03DAh
	(64310) reserved (0)
 5	vertical retrace status
	=0 PORTIBM PC Portable (uses same BIOS as XT) 03BAh/03DAh bit 3 is vertical retrace (CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA./EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors./VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	=1 PORTIBM PC Portable (uses same BIOS as XT) 03BAh/03DAh bit 3 is video active (MDA(Monochrome Display Adapter) A text-only video adapter introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also CGAColor Graphics Adapter, HGC./Herc)
 4-0	(64310) reserved (0)
 4	(64200) display enable status
	=0 PORTIBM PC Portable (uses same BIOS as XT) 03BAh/03DAh bit 0 is display enable (CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA./EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors./VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
	=1 PORTIBM PC Portable (uses same BIOS as XT) 03BAh/03DAh bit 0 is HSync (MDA(Monochrome Display Adapter) A text-only video adapter introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also CGAColor Graphics Adapter, HGC./Herc)
 3-2	(64200) (read-only) Hercules configuration register readback
	  (see PORTIBM PC Portable (uses same BIOS as XT) 03BFh)
 1-0	(64200) emulation mode
	00 VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.
	01 CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA.
	10 MDA(Monochrome Display Adapter) A text-only video adapter introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also CGAColor Graphics Adapter, HGC./Hercules
	11 EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors.
SeeAlso: #P0762,#P0763


Bitfields for Chips&Technologies "XR15" Write Protect register:
Bit(s)	Description	(Table P0785)
 7	write protect AR11 (both bits 7 and 0 must be clear to write AR11)
 6
 5
 4
 3
 2
 1
 0	!!!chips\64200.pdf p.82
SeeAlso: #P0762


Bitfields for Chips&Technologies 64310 "XR16" vertical overflow register:
Bit(s)	Description	(Table P0786)
 7	resrved (0)
 6	line compare bit 10
 5	resrved (0)
 4	vertical blank start bit 10
 3	resrved (0)
 2	vertical sync start bit 10
 1	vertical display enable end bit 10
 0	vertical total bit 10
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR17" horizontal overflow register:
Bit(s)	Description	(Table P0787)
 7	half line compare bit 8 (bits 7-0 in XR19)
 6	overflow end bits (XR17 bits 5 and 3) enable
 5	horizontal blank end bit 6
 4	horizontal blank start bit 8
 3	horizontal sync end bit 5
 2	horizontal sync start bit 8
 1	horizontal display enable end bit 8
 0	horizontal total bit 8
SeeAlso: #P0763


Bitfields for Chips&Technologies "XR19" alt. horizontal sync start/half-line:
Bit(s)	Description	(Table P0788)
 7-0	(64310) CRT half-line value
SeeAlso: #P0763


Bitfields for Chips&Technologies "XR1A" Alternate Horizontal Sync End register:
Bit(s)	Description	(Table P0789)
 7
 6-5
 4-0
SeeAlso: #P0762,#P0790


Bitfields for Chips&Technologies "XR1D" Alternate Horizontal Blank End reg:
Bit(s)	Description	(Table P0790)
 7
 6-5
 4-0
SeeAlso: #P0762,#P0789


Bitfields for Chips&Technologies "XR1F" Virtual EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors. Switch register:
Bit(s)	Description	(Table P0791)
 7
 6-4	reserved (0)
 3-0	virtual EGAEnhanced Graphics Adapter(Enhanced Graphics Adapter) IBMInternational Busiuness Machines's second color video board for the IBMInternational Busiuness Machines PCIBM PC family, capable of a maximum resolution of 640x350 pixels in 16 simultaneous colors of a total of 64 possible colors. switches
SeeAlso: #P0762


Bitfields for Chips&Technologies "XR28" Video Interface register:
Bit(s)	Description	(Table P0792)
 7	reserved
 6	(64310) wide video pixel panning (if bit 4 = 1 and port 3C0h
	  register 10h bit 6 = 1)
	0 = pixel panning controlled by port 3C0h register 13h bits 2-1
	1 = pixel panning controlled by port 3C0h register 13h bits 2-0
 5	interlaced video
 4	(64310) wide video path (doubles values in all horizontal CRTC
	  registers)
	0 = 4-bit video data path
	1 = 8-bit video data path (horizontal pixel panning controlled by
	  bit 6; port 3CEh register 5h bit 5 must be 0)
 3	reserved (0)
 2	shut off video
 1	(64310) BLANK#/display enable select
	0 = BLANK# pin outputs BLANK#
	1 = BLANK# pin outputs display enable
 0	(64310) BLANK#/display enable polarity
	0 = negative polarity
	1 = positive polarity
SeeAlso: #P0762,#P0763


Bitfields for Chips&Technologies 64310 "XR30" clock divide control register:
Bit(s)	Description	(Table P0793)
 7-4	reserved (0)
 3-1	post divisor select
	000 = divide by 1
	001 = divide by 2
	010 = divide by 4
	011 = divide by 8
	100 = divide by 16
	101 = divide by 32
	110-111 = reserved
 0	reference divisor select
	0 = divide by 4
	1 = divide by 1
Note:	Registers XR30-32 are used to program either memory clock or video
	  clock VCO, selected by XR33 bit 5. Data must be written in sequence
	  to all three registers, after which they are transferred to VCO
	  simultaneously.
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR31" clock M-divisor register:
Bit(s)	Description	(Table P0794)
 7	reserved (0)
 6-0	VCO M-divisor (program value - 2)
Note:	Registers XR30-32 are used to program either memory clock or video
	  clock VCO, selected by XR33 bit 5. Data must be written in sequence
	  to all three registers, after which they are transferred to VCO
	  simultaneously.
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR32" clock N-divisor register:
Bit(s)	Description	(Table P0795)
 7	reserved (0)
 6-0	VCO N-divisor (program value - 2)
Note:	Registers XR30-32 are used to program either memory clock or video
	  clock VCO, selected by XR33 bit 5. Data must be written in sequence
	  to all three registers, after which they are transferred to VCO
	  simultaneously.
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR33" clock control register:
Bit(s)	Description	(Table P0796)
 7-6	reserved (0)
 5	clock register program pointer
	0 = VCLK VCO
	1 = MCLK VCO
 4	PCLK equals MCLK instead of VCLK
 3	reserved (0)
 2	OSC enable (if XR01 bit 5 = 1)
 1	MCLK VCO enable (if XR01 bit 4 = 1)
 0	VCLK VCO enable (if XR01 bit 4 = 1)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR3A" color key compare data 0:
Bit(s)	Description	(Table P0797)
 7-0	color compare data 0
	(Compared to lowest 8 bits of 64310 memory data, masked with XR3D. If
	  match occurs and XR06 bit 4 = 1, external video is sent to screen.
	  Color comparison occurs before RAMDAC. Palette LUT index is used in
	  4BPP and 8BPP modes.)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR3B" color key compare data 1:
Bit(s)	Description	(Table P0798)
 7-0	color compare data 1
	(Compared to bits 15-8 of 64310 memory data, masked with XR3E. If
	  match occurs and XR06 bit 4 = 1, external video is sent to screen.
	  This register should be masked in 4BPP and 8BPP modes by setting
	  XR3E to FFh.)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64200 "XR3C" Serial/Row Count register:
Bit(s)	Description	(Table P0799)
 7-6	reserved (0)
 5-3	row count (number of transfer cycles)
	000 = 64
	001 = 128
	010 = 256
	011 = 512
	1x0 = 1024
	1x1 = 2048
 2-0	serial count (same as for bits 5-3, but in units of serial clocks)
SeeAlso: #P0762,#P0801,#P0768


Bitfields for Chips&Technologies 64310 "XR3C" color key compare data 2:
Bit(s)	Description	(Table P0800)
 7-0	color compare data 2
	(Compared to bits 23-16 of 64310 memory data, masked with XR3F. If
	  match occurs and XR06 bit 4 = 1, external video is sent to screen.
	  This register should only be used in 24BPP modes, and masked in
	  other modes by setting XR3F to FFh.)
SeeAlso: #P0763,#P0802


Bitfields for Chips&Technologies 64200 "XR3D" Multiplexer Mode register:
Bit(s)	Description	(Table P0801)
 7-5	reserved
 4
 3
 2-0	multiplexer mode
SeeAlso: #P0762,#P0799,#P0768


Bitfields for Chips&Technologies 64310 "XR3D" color key compare mask 0:
Bit(s)	Description	(Table P0802)
 7-0	color compare mask 0 (masks XR3A)
	0 = bit compared
	1 = bit masked from comparison
SeeAlso: #P0763,#P0800,#P0803


Bitfields for Chips&Technologies 64310 "XR3E" color key compare mask 1:
Bit(s)	Description	(Table P0803)
 7-0	color compare mask 1 (masks XR3B)
	0 = bit compared
	1 = bit masked from comparison
SeeAlso: #P0763,#P0802,#P0804


Bitfields for Chips&Technologies 64310 "XR3F" color key compare mask 2:
Bit(s)	Description	(Table P0804)
 7-0	color compare mask 2 (masks XR3C)
	0 = bit compared
	1 = bit masked from comparison
SeeAlso: #P0763,#P0802,#P0803


Bitfields for Chips&Technologies 64310 "XR40" BitBlt config register:
Bit(s)	Description	(Table P0805)
 7-2	reserved (0)
 1-0	BitBlt draw mode
	00 = reserved
	01 = 8bpp
	10 = 16bpp
	11 = reserved
	(24bpp handled in 8bpp mode; no nibble mode for 4bpp)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR52" refresh control register:
Bit(s)	Description	(Table P0806)
 7-3	reserved (0)
 2-0	VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. refresh cycles per scan line
	000 = default
	001-101 = 1-5 refresh cycles
	110-111 = illegal
SeeAlso: #P0763


Bitfields for Chips&Technologies "XR70" Setup/Disable Control register:
Bit(s)	Description	(Table P0807)
 7
 6-0	reserved (0)
SeeAlso: #P0762


Bitfields for Chips&Technologies 64310 "XR71" GPIO control register:
Bit(s)	Description	(Table P0808)
 7-5	GPOE
	0 = respective GPIO pin is input
	1 = respective GPIO pin is output
	(if standard feature connector is enabled (XR73 bit 5 = 1), GPIO pin 5
	  becomes an alternate fixed function input (ECLK#) and bit 5 must be
	  set to 0)
	(if external clock is selected (XR01 bit 4 = 0), bits 7-6 have no
	  effect and GPIO pins 7-6 become CLKSEL1-0 and output contents of
	  port 3CCh bits 3-2)
 4	reserved (0)
 3-2	GPOE
	0 = respective GPIO pin is input
	1 = respective GPIO pin is output
	(if standard feature connector is enabled (XR73 bit 5 = 1), GPIO pins
	  3 and 2 become alternate fixed function inputs (EVIDEO#, ESYNC#) and
	  bits 3-2 must be set to 0)
 1-0	reserved (0)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR72" GPIO data register:
Bit(s)	Description	(Table P0809)
 7-5	GPIO (input from/output to respective GPIO pin)
	(if standard feature connector is enabled (XR73 bit 5 = 1), GPIO pin 5
	  becomes an alternate fixed function input (ECLK#))
	(if external clock is selected (XR01 bit 4 = 0), GPIO pins 7-6 become
	  CLKSEL1-0 and output contents of port 3CCh bits 3-2)
 4	reserved (0)
 3-2	GPIO (input from/output to respective GPIO pin)
	(if standard feature connector is enabled (XR73 bit 5 = 1), GPIO pins
	  3 and 2 become alternate fixed function inputs (EVIDEO#, ESYNC#))
 1-0	reserved (0)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR73" misc control register:
Bit(s)	Description	(Table P0810)
 7	ROMCS# write access enable
 6	external color key enable
 5	standard feature connector enable (must be set before XR06 bit 0)
 4	reserved (0)
 3	VSYNC control
	0 = CRTC VSYNC is output on VSYNC pin 126
	1 = bit 2 is output on VSYNC pin 126
 2	VSYNC data (if bit 3 = 1, this bit will be output on VSYNC pin)
 1	HSYNC control
	0 = CRTC HSYNC is output on HSYNC pin 125
	1 = bit 0 is output on HSYNC pin 125
 0	HSYNC data (if bit 1 = 1, this bit will be output on HSYNC pin)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR74" configuration register 2:
Bit(s)	Description	(Table P0811)
 7-0	(64300) ???
	(64310) reserved (0)
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR7A" test index register:
Bit(s)	Description	(Table P0812)
 7-0	test index (select XR7B function)
	00h = reserved
	01h = CRC signature analysis
	02h-FFh = reserved
SeeAlso: #P0763


Bitfields for Chips&Technologies 64310 "XR7B" test control register:
Bit(s)	Description	(Table P0813)
---XR7A = 01h---
 7	CRC status (read-only)
	0 = CRC ARM=0 or CRC data is being generated (CRC data should not be
	  read)
	1 = CRC ARM=1 and CRC data is ready
 6	CRC arm
	1 = arm CRC generation to start after the next VSYNC and stop after the
	  VSYNC following that (should not be set to 0 until entire CRC value
	  is read)
 5-4	CRC data select (select data to be read from XR7C)
	00 = CRC bit 7-0
	01 = CRC bits 15-8
	10 = 0 and CRC bits 22-16
	11 = 00h
 3-2	CRC qualification
	00 = take all data
	01 = take data when not blank (DE + overscan)
	10 = take data when DE is active
	11 = take data in PCIBM PC Video window only
 1-0	video data select
	00 = red video data before DAC(Digital-to-Analog Converter) A hardware device (in its simplest form, nothing more than a set of interconnected resistors) which converts a digital number into an analog signal whose voltage is proportional to the value of the digital number.  VGAVideo Graphics Array and later color video boards use DACs to convert color values into the analog signals sent to the display; sound boards normally use DACs as well. output
	01 = green video data before DAC(Digital-to-Analog Converter) A hardware device (in its simplest form, nothing more than a set of interconnected resistors) which converts a digital number into an analog signal whose voltage is proportional to the value of the digital number.  VGAVideo Graphics Array and later color video boards use DACs to convert color values into the analog signals sent to the display; sound boards normally use DACs as well. output
	10 = blue video data before DAC(Digital-to-Analog Converter) A hardware device (in its simplest form, nothing more than a set of interconnected resistors) which converts a digital number into an analog signal whose voltage is proportional to the value of the digital number.  VGAVideo Graphics Array and later color video boards use DACs to convert color values into the analog signals sent to the display; sound boards normally use DACs as well. output
	11 = control data (VSYNC, HSYNC, blank, internal display enable,
	  0, 0, 0, 0)
SeeAlso: #P0763,#P0812


Bitfields for Chips&Technologies 64310 "XR7C" test data register:
Bit(s)	Description	(Table P0814)
---XR7A = 01h---
 7-0	CRC data (read-only)
SeeAlso: #P0763,#P0812


Bitfields for Chips&Technologies "XR7E" CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA. Color Select register:
Bit(s)	Description	(Table P0815)
 7-6	reserved
 5
 4
 3-0
Note:	this is a mirror of the register accessed via PORTIBM PC Portable (uses same BIOS as XT) 03D9h, which is
	  always visible, while PORTIBM PC Portable (uses same BIOS as XT) 03D9h is only visible in CGAColor Graphics Adapter(Color/Graphics Adapter) One of the two video display boards introduced together with the original IBMInternational Busiuness Machines PCIBM PC.  See also HGC, MDA. emulation
SeeAlso: #P0762,PORTIBM PC Portable (uses same BIOS as XT) 03D9h


Bitfields for Chips&Technologies "XR7F" Diagnostic register:
Bit(s)	Description	(Table P0816)
 7	special test function (should remain cleared)
 6	enable test function in bits 5-2
 5-2	test function
 1	tri-state output pins: !!!
 0	tri-state output pins: !!! chips\64200.pdf p.90
SeeAlso: #P0762