PORTIBM PC Portable (uses same BIOS as XT) 03C4-03C5 - 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. - SEQUENCER REGISTERS
Range:	PORTIBM PC Portable (uses same BIOS as XT) 03C4h or PORTIBM PC Portable (uses same BIOS as XT) 02C4h (alternate 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: PORTIBM PC Portable (uses same BIOS as XT) 03C0h,PORTIBM PC Portable (uses same BIOS as XT) 03C2h,PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Cirrus",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"S3"
SeeAlso: PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Tseng",PORTIBM PC Portable (uses same BIOS as XT) 03C6h,PORTIBM PC Portable (uses same BIOS as XT) 03D0h

03C4  -W  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.	TS index register
		bit7-3 : reserved (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. only)
		bit2-0 : current TS index
03C4  RW  VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.	sequencer register index (see #P0670)
03C5  -W  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.	TS data register
03C5  RW  VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.	sequencer register data


(Table P0670)
Values for 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. indexed TS (sequencer) registers:
 00h	reset register
	bit7-2 : reserved
	bit1 =0: synchronous reset (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.)
	bit0 =0: asynchronous reset (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., ET4000)
		 synchronous reset, also (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.)
 01h	clocking mode register / TS mode (see #P0671)
 02h	map mask register (see #P0672)
 03h	character map select register / font select (see #P0673)
 04h	memory mode register (see #P0674)
 07h	(undoc VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) reset horizontal character counter
	any write to this register holds horizontal character counter at 00h
	  until any other sequencer register is written
Note:	register 07h is documented in the C&T Wingine documentation
SeeAlso: #P0675,#P0696,#P0685


Bitfields for 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. sequencer clocking mode register:
Bit(s)	Description	(Table P0671)
 7-6	reserved
 5	(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: screen refresh off
 4	(VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) shift load (0=4x8, 1=1x32)
 3	internal character clock (0=normal, 1=dotclock/2)
 2	serial shift video load (0=4x8, 1=2x16)
 1	(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.) CRTC bandwidth (0=4/5, 1=2/5)
 0	dot clocks per character (0=9, 1=8) (ET4000: see 06h)
SeeAlso: #P0670


Bitfields for 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. sequencer map mask register:
Bit(s)	Description	(Table P0672)
 7-4	reserved
 4	Genoa SuperEGA only: plane4 ???
 3	write enable display memory plane 3
 2	write enable display memory plane 2
 1	write enable display memory plane 1
 0	write enable display memory plane 0
SeeAlso: #P0670


Bitfields for 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. sequencer character map select register:
Bit(s)	Description	(Table P0673)
 7-6	reserved
 5	(VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit3 for second text-font
 4	(VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) bit3 for first text-font
 3-2	second text-font (attr bit3=1)
 1-0	first text-font (attr bit3=0)
	offset in font memory (4-7: VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. only)
	   0 00b =  0KB
	   0 01b = 16KB
	   0 10b = 32KB
	   0 11b = 48KB
	   1 00b =  8KB
	   1 01b = 24KB
	   1 10b = 40KB
	   1 11b = 56KB
SeeAlso: #P0670


Bitfields for 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. sequencer memory mode register:
Bit(s)	Description	(Table P0674)
 7-4	reserved
 3	=1 (VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers.) enable chain 4 linear graphics mode
	(when set, low two bits of CPU(Central Processing Unit) The microprocessor which executes programs on your computer. address select the plane)
 2	addressing mode
	0 odd/even mode (even addresses access planes 0/2, odd planes 1/3)
	1 sequential mode
 1	=1 extended memory (0=64KB, 1=more)
 0	(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.) 1=textmode, 0=graphics mode
SeeAlso: #P0670
                                                                                


PORTIBM PC Portable (uses same BIOS as XT) 03C4-03C5 - Cirrus Logic GRAPHICS - EXTENDED SEQUENCER REGISTERS
SeeAlso: PORTIBM PC Portable (uses same BIOS as XT) 03C4h"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.",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"S3",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Tseng"

03C4  RW  sequencer register index (see #P0696)
03C5  RW  sequencer register data


(Table P0675)
Values for Cirrus CL-GD7556 extended sequencer registers:
 00h-04h same as 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. (see #P0670) 
 06h	"SR6" key register -- enable access to extension registers
	set to xxx1x010 to unlock extended sequencer and CRTC registers
 07h	"SR7" extended sequencer mode (see #P0676)
 08h	"SR8" DDC2B control (see #P0677)
 09h	"SR9" scratch pad #0
 0Ah	"SRA" scratch pad #1
 0Bh	"SRB" VCLK0 numerator  !!!gd7556hrm.pdf p.239
 0Ch	"SRC" VCLK1 numerator
 0Dh	"SRD" VCLK2 numerator
 0Eh	"SRE" VCLK3 numerator
 0Fh	"SRF" display memory control (see #P0678)
 10h	"SR10" hardware cursor/icon coarse horizontal position
 11h	"SR11" hardware cursor/icon coarse vertical position
 12h	"SR12" hardware cursor attributes
 13h	"SR13" hardware cursor pattern address
 14h	"SR14" scratch pad #2
 15h	"SR15" scratch pad #3
 17h	"SR17" BitBLT memory map I/O address
 18h	"SR18" signature generator control
 19h	"SR19" signature generator result (low)
 1Ah	"SR1A" signature generator result (high)
 1Bh	"SR1B" VLK0 denominator/post scaler
 1Ch	"SR1C" VLK1 denominator/post scaler
 1Dh	"SR1D" VLK2 denominator/post scaler
 1Eh	"SR1E" VLK3 denominator/post scaler
 1Fh	"SR1F" MCLK frequency / VCLK source select
 20h	"SR20" miscellaneous control 2
 21h	"SR21" test bus control
 22h	"SR22" hardware configuration read 1
 23h	"SR23" software configuration 1
 24h	"SR24" flat panel type switches enable
 25h	"SR25" FasText™ mode control
 26h	"SR26" shader signature (low)
 27h	"SR27" shader signature (high)
 28h	"SR28" scratch pad #4
 29h	"SR29" scratch pad #5
 2Ah	"SR2A" hardware icon #0 control
 2Bh	"SR2B" hardware icon #1 control
 2Ch	"SR2C" hardware icon #2 control / byte-swap enable
 2Dh	"SR2D" hardware icon #3 control / cursor memory access
 2Eh	"SR2E" hardware cursor horizontal position extension
 2Fh	"SR2F" half-frame accel. FIFO threshold for surrounding graphics
 32h	"SR32" half-frame accel. FIFO threshold in video window
 33h	"SR33" spare register
 34h	"SR34" Host CPU(Central Processing Unit) The microprocessor which executes programs on your computer. cycle stop control
Note:	the scratch pad registers are reserved for use by the VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. 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.
SeeAlso: #P0670,#P0685,#P0696


Bitfields for Cirrus CL-GD7556 extended sequencer mode register:
Bit(s)	Description	(Table P0676)
 7-4	display memory segment
 3-1	CRT Controller character clock divisor
 0	select high-resolution packed-pixel mode
!!!gd7556hrm.pdf p.234
SeeAlso: #P0675


Bitfields for Cirrus CL-GD7556 DDC2B Control register:
Bit(s)	Description	(Table P0677)
 7	DDCD output status (read-only)
 6-3	reserved
 2	DDCC output status (read-only)
 1	DDCD (I2C(also IIC; the "2" is superscripted) Inter-Integrated Circuit Bus -- A moderate-speed serial communications bus originally invented by Philips in the early 1980s for consumer-electronics applications, such as inter-chip communication in a television set or high-end stereo.	 The I2C bus has recently appeared on PCs in video capture boards and similar devices, as well as (surprisingly) SDRAM DIMMs (for the on-board serial EEPROM).  The ACCESS.bus is a derivative of the I2C bus which forms the physical layer of the Universal Serial Bus.	 Similary, the SMBus (System Management Bus) also uses I2C as its physical layer. SDAsee Swappable Data Area) output control
 0	DDCC (I2C(also IIC; the "2" is superscripted) Inter-Integrated Circuit Bus -- A moderate-speed serial communications bus originally invented by Philips in the early 1980s for consumer-electronics applications, such as inter-chip communication in a television set or high-end stereo.	 The I2C bus has recently appeared on PCs in video capture boards and similar devices, as well as (surprisingly) SDRAM DIMMs (for the on-board serial EEPROM).  The ACCESS.bus is a derivative of the I2C bus which forms the physical layer of the Universal Serial Bus.	 Similary, the SMBus (System Management Bus) also uses I2C as its physical layer. SCL) output control
Notes:	bits 1 and 0 are used to drive the I2C(also IIC; the "2" is superscripted) Inter-Integrated Circuit Bus -- A moderate-speed serial communications bus originally invented by Philips in the early 1980s for consumer-electronics applications, such as inter-chip communication in a television set or high-end stereo.	 The I2C bus has recently appeared on PCs in video capture boards and similar devices, as well as (surprisingly) SDRAM DIMMs (for the on-board serial EEPROM).  The ACCESS.bus is a derivative of the I2C bus which forms the physical layer of the Universal Serial Bus.	 Similary, the SMBus (System Management Bus) also uses I2C as its physical layer. bus used for DDC communications;
	  bits 7 and 2 are used to read back the current state of the bus lines
	SR24 bit 7 must be cleared to enable access to the bus
SeeAlso: #P0675,#M0079,I2C(also IIC; the "2" is superscripted) Inter-Integrated Circuit Bus -- A moderate-speed serial communications bus originally invented by Philips in the early 1980s for consumer-electronics applications, such as inter-chip communication in a television set or high-end stereo.	 The I2C bus has recently appeared on PCs in video capture boards and similar devices, as well as (surprisingly) SDRAM DIMMs (for the on-board serial EEPROM).  The ACCESS.bus is a derivative of the I2C bus which forms the physical layer of the Universal Serial Bus.	 Similary, the SMBus (System Management Bus) also uses I2C as its physical layer. A0h"DDC"


Bitfields for Cirrus CL-GD7556 Display Memory Control register:
Bit(s)	Description	(Table P0678)
 7	bank select for display memory
 6	!!!gd7556hrm.pdf p.241
 5	reserved
 4-3	display memory data width
 2	RAS# cycle select for display memory
 1	display memory configuration symmetry
 0	multiple-CAS# / multiple-WE# select for display memory
SeeAlso: #P0823
                                                                                


PORTIBM PC Portable (uses same BIOS as XT) 03C4-03C5 - NVIDIA - EXTENDED SEQUENCER REGISTERS
SeeAlso: PORTIBM PC Portable (uses same BIOS as XT) 03C4h"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.",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"S3",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Tseng"

03C4  RW  sequencer register index (see #P0679)
03C5  RW  sequencer register data


(Table P0679)
Values for NVIDIA NV3/RIVA128 extended sequencer registers:
 06h	key register (enable access to extended registers when set to 57h,
	  disable access when set to any other value)
 19h	extended start address and offset
	bits 7-5: offset bits 10-8
	bits 4-0: address bits 20-16
 1Ah	flags (see #P0680)
 1Bh	refresh FIFO control (see #P0681)
 20h	FIFO watermark (see #P0682)
 25h	miscellaneous extension bits (see #P0683)
 28h	framebuffer format
 2Dh	extended horizontal bits (see #P0684)
 30h	graphics cursor control 0
 31h	graphics cursor control 1
 ???


Bitfields for NVIDIA NV3 flags:
Bit(s)	Description	(Table P0680)
 !!!nv3ref.h
SeeAlso: #P0679


Bitfields for NVIDIA NV3 refresh FIFO control:
Bit(s)	Description	(Table P0681)
 7	underflow warning
 2-0	burst length
	000 eight
	001 32
	010 64
	011 128
	100 256
SeeAlso: #P0679,#P0682


Bitfields for NVIDIA NV3 FIFO watermark:
Bit(s)	Description	(Table P0682)
 7	reset FIFO
 5-0	watermark, in eight-byte units (refresh FIFO will start refilling
	  when occupancy falls below twice this value)
SeeAlso: #P0679,#P0681


Bitfields for NVIDIA NV3 miscellaneous extension bits:
Bit(s)	Description	(Table P0683)
 5	offset bit 11
 4	horizontal blanking end, bit 6
 3	vertical blanking start, bit 10
 2	vertical retrace start, bit 10
 1	vertical display end, bit 10
 0	vertical total, bit 10
SeeAlso: #P0679,#P0684


Bitfields for NVIDIA NV3 extended horizontal bits:
Bit(s)	Description	(Table P0684)
 4	"inter_half_start" bit 8
 3	horizontal retrace start, bit 8
 2	horizontal blanking start, bit 8
 1	display end, bit 8
 0	display total, bit 8
SeeAlso: #P0679,#P0683
                                                                                


PORTIBM PC Portable (uses same BIOS as XT) 03C4-03C5 - S3 GRAPHICS - EXTENDED SEQUENCER REGISTERS
SeeAlso: PORTIBM PC Portable (uses same BIOS as XT) 03C4h"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.",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Cirrus",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Tseng",PORTIBM PC Portable (uses same BIOS as XT) 03C4"NVIDIA"

03C4  RW  sequencer register index (see #P0685)
03C5  RW  sequencer register data


(Table P0685)
Values for S3 extended sequencer registers:
 00h-04h same as 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. (see #P0670) 
 08h	S3 864/964/765 (Trio64V): key register -- enable access to S3 extended
	  registers when set to x6h
---S3 Trio32/Trio64/Trio64V+ ---
 09h	"SR9" MMIO-Only
	bit 7: disable port I/O when memory-mapped I/O is enabled
	bits 6-0: reserved
	bit 1: ??? (set by Stealth64 Video 2001)
 0Ah	"SRA" external bus request control register (see #P0686)
 0Bh	"SRB" miscellaneous extended sequencer register (see #P0687)
 0Dh	"SRD" VSYNC/HSYNC control (see #P0689)
 10h	"SR10" MCLK value (low) (see #P0690)
 11h	"SR11" MCLK value (high) (see #P0691)
 12h	"SR12" DCLK value (low) (see #P0690)
 13h	"SR13" DCLK value (high) (see #P0691)
 14h	"SR14" CLKSYN control 1 (see #P0692)
 15h	"SR15" CLKSYN control 2 (see #P0693)
 16h	"SR16" CLKSYN Test (high) (reserved for testing of clock synth)
 17h	"SR17" CLKSYN Test (low) (reserved for testing of clock synth)
 18h	"SR18" RAMDAC/CLKSYN Control (see #P0694)
---S3 Trio64V+ ---
 1Ch	"SR1C" signal select (see #P0695)
SeeAlso: #P0670,#P0675,#P0696


Bitfields for S3 Trio32/64/64V+ "SRA" external bus request control register:
Bit(s)	Description	(Table P0686)
 7	fast CPU(Central Processing Unit) The microprocessor which executes programs on your computer. writes
	when set and MCLK is less than 57 MHz, CPU(Central Processing Unit) The microprocessor which executes programs on your computer. writes take 2 MCLKs instead
	  of 3 MCLKs (for MCLKs of 55-57 MHz, SR15 bit 7 should also be set)
 6	(Trio64) Pin50 function select
	=0 (CR36 bit 2=1) Pin50 outputs a second -OE0 signal
	=1 (CR36 bit 2=1) Pin50 outputs -RAS1
 5	=0 tri-state pixel-data lines (reduces power consumption)
 4-0	maximum 2*MCLKs that secondary memory controllers are granted access to
	  Trio's memory bus
Note:	bit 6 must be set for 4M fast page-mode memory; it has no effect if
	  EDO memory is selected via CR36 bit 2
SeeAlso: #P0685


Bitfields for S3 Trio32/64/64V+ "SRB" misc extended sequencer register:
Bit(s)	Description	(Table P0687)
 7-4	alternate color mode (for feature connector input) (see #P0688)
 3	(Trio32 only) enable packed 24 bpp (mode 12); also requires CR67 bits
		  7-4=0000
 2	reserved
 1	VAFC clocking
	=0 latch pixel data from pass-through feature connector on VCLK
	=1 latch pixel data from VAFC on VCLKI
 0	dot clock select (testing only)
	=0 use internal dot clock
	=1 use VCLKI
SeeAlso: #P0685,#P0751


(Table P0688)
Values for S3 Trio32/Trio64 color mode:
0000	mode 0 = 8-bit, 1 pixel/VCLK
0001	mode 8 = 8-bit, 2 pixels/VCLK
0011	mode 9 = 15-bit, 1 pixel/VCLK
0101	mode 10 = 16-bit, 1 pixel/VCLK
0111	mode 12 = 640x480x24-bit (packed), 1 pixel/3 DCLKs (Trio32 only)
1101	mode 13 = 24-bit, 1 pixel/VCLK
else	reserved
Note:	mode 8 also requires SR18 bit 7=1 and either SR15 bit 4=1 or
	  SR15 bit 6=1
SeeAlso: #P0687,#P0751


Bitfields for S3 "SRD" Trio32/Trio64 VSYNC/HSYNC control:
Bit(s)	Description	(Table P0689)
 7-6	vertical sync control
	00 normal operation
	01 force to 0
	10 force to 1
	11 reserved
 5-0	horizontal sync control (settings as for vsync)
 3-1	reserved
 1	(Trio64V+) feature connector type
	=0 Trio64-compatible
	=1 new LPB type
 0	enable feature connector
Note:	bits 7-4 are used to select the DPMSsee DOS Protected-Mode Services power mode as follows:
	    0000 On
	    0001 Standby
	    0100 Suspend
	    0101 Off
SeeAlso: #P0685


Bitfields for S3 Trio32/Trio64 "SR10"/"SR12" MCLK/DCLK value (low):
Bit(s)	Description	(Table P0690)
 7	reserved
 6-5	PLL R value
 4-0	PLL N-divider value
SeeAlso: #P0691,#P0685


Bitfields for S3 Trio32/Trio64 "SR11"/"SR13" MCLK/DCLK value (high):
Bit(s)	Description	(Table P0691)
 7	reserved
 6-0	PLL M-divider value
SeeAlso: #P0690,#P0685


Bitfields for S3 Trio32/Trio64 "SR14" CLKSYN control 1:
Bit(s)	Description	(Table P0692)
 7	select external DCLK (testing only; also requires external strapping)
 6	select external MCLK (testing only)
 5	select Pin146 function
	=0 use as -STRD
	=1 tri-state output; use as input (required to enable bit 6)
 4	clear clock synthesizer counters (testing only)
 3	"M TEST" MCLK test
	=0 test DCLK
	=1 test MCLK
 2	enable clock synthesizer counters (testing only)
 1	power down MCLK PLL (testing only)
 0	power down DCLK PLL (testing only)
SeeAlso: #P0693,#P0685


Bitfields for S3 Trio32/Trio64 "SR15" CLKSYN control 2:
Bit(s)	Description	(Table P0693)
 7	enable fast memory writes (2 MCLKs instead of 3 MCLKs) by bypassing
	  VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers. lienar addressing logic (requires SRA bit 7 set)
 6	invert DCLK
 5	load MCLK and DCLK immediately on transition from 1 to 0
 4	divide DCLK by 2
 3	VLCK direction
	=0 Pin148 always outputs internal VCLK
	=1 -EVCLK signal determines VLCK direction
 2	MCLK output (testing only)
	=0 Pin147 acts as STWR strobe
	=1 Pin147 outputs internal MCLK
 1	enable new DCLK frequency load (asynchronous)
 0	enable new MCLK frequency load
Notes:	bits 1 and 5 also require that PORTIBM PC Portable (uses same BIOS as XT) 03C2h bits 3-2=11
	bit 5 must never be left set; it should only be pulsed to cause the
	  MCLK/DCLK load
	bit 0 should be cleared after loading the new MCLK value to avoid
	  repeated loading
	either bit 4 or 6 must be set for clock-doubled RAMDAC operation
	  (see #P0686)
SeeAlso: #P0692,#P0694,#P0685


Bitfields for S3 Trio32/Trio64 "SR18" RAMDAC/CLKSYN control:
Bit(s)	Description	(Table P0694)
 7	enable clock-doubled mode (see also #393)
 6	fast LUT write cycle (1 DCLK instead of default 2 DCLKs)
 5	power down RAMDAC (RAMDAC memory is retained even when powered down)
 4	(testing only) place blue data on internal data bus
 3	(testing only) place green data on internal data bus
 2	(testing only) place red data on internal data bus
 1	(testing only) reset RAMDAC test counter
 0	(testing only) enable test counter
SeeAlso: #P0693


Bitfields for S3 Trio64V+ "SR1C" signal select:
Bit(s)	Description	(Table P0695)
 7-2	reserved
 1-0	signal select
	VL-Bus:
	    00 Pin151 is ENFEAT#, Pin153 is ROMCS# (default)
	    01 Pin151 is GPIOSTR#, Pin153 is ROMCS#
	    10 Pin151 is GOP0, Pin153 is ROMCS#
	    11 Pin151 is GOP0, Pin153 is GOP1
	PCI:
	    00 Pin151 is ENFEAT#, Pin190 is STWR#, Pin153 is ROMEN# (default)
	    01 Pin151 is reserved, Pin190 is STWR#, Pin153 is ROMEN#
	    1x Pin151 is GOP0, Pin190 is GOP1, Pin153 is ROMEN#
SeeAlso: #P0073
                                                                                


PORTIBM PC Portable (uses same BIOS as XT) 03C4-03C5 - Tseng Labs GRAPHICS - EXTENDED SEQUENCER REGISTERS
SeeAlso: PORTIBM PC Portable (uses same BIOS as XT) 03C4h"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.",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"Cirrus",PORTIBM PC Portable (uses same BIOS as XT) 03C4h"S3"

03C4  RW  sequencer register index (see #P0696)
03C5  RW  sequencer register data


(Table P0696)
Values for Tseng Labs extended sequencer registers:
 00h-04h same as 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. (see #P0670)
 06h	ET3000 only: Zoom control register
 06h	ET4000 only: TS state control (protected by 'key')
	bit7-3 : reserved
	bit2-1 : timing sequencer state bit2-1
		   (bit0 is bit0 TS mode register)
		   00 0b=  9 dots
		   00 1b=  8 dots
		   01 0b= 10	  (10-16 are ET4000 only)
		   01 1b= 11
		   10 0b= 12
		   11 1b= 16
	bit0	: reserved
 07h	ET3000/ET4000 only: TS auxiliary mode (see #P0697)
SeeAlso: #P0670,#P0675,#P0685


Bitfields for ET3000/ET4000 sequencer auxiliary mode:
Bit(s)	Description	(Table P0697)
 7	compatibility mode (1=VGAVideo Graphics Array(Video Graphics Array) The video adapter introduced with the IBMInternational Busiuness Machines PS/2IBM PS/2, any model series of computers., 0=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.)
 6	select MCLK/2 (with bit0=0)
 5	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. ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. address map 2
 4	reserved
 3	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. ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. address map 1
 2	reserved (1)
 1	select SCLK input from MCLK
 0	select MCLK/4 (with bit6=1)
 5+3	ROM(Read-Only Memory) A memory for program storage which may not be changed by the program as it runs. address
	00 C0000-C3FFF
	01 disabled
	10 C0000-C5FFF, C6800-C7FFF
	11 C0000-C7FFF (default)
Notes:	at least on the ET4000, this register is protected by a 'key'
	this register is also supported by ET3000, but the above description
	  is based on the ET4000
SeeAlso: #P0670