cmos.lst

A Programmer s Reference to BIOS, DOS, and Third-Party Calls

CMOS 1Ch - MCA - SLOT 1 ADAPTER CARD ID
----------R1C--------------------------------
CMOS 1Ch - AMI - First Hard Disk user defined: # of Cylinders, High Byte
----------R1C--------------------------------
CMOS 1Ch - PHOENIX - MSB of Word to 82335 RC1 roll compare register
--------y-R1C--------------------------------
CMOS 1Ch,1Dh - AWARD - Password
Note:	Stored as a checksum using the following algorithm:
	    initialize 16-bit checksum to zero
	    for each ASCII character between 32 (space) and 127 (DEL) in the
	      password,	add character to checksum, then rotate left two bits
	    store low byte of result in 1Ch and high byte in 1Dh (for user
	      password, use locations 4Dh and 4Eh instead)
SeeAlso: CMOS 4Dh"AWARD"
----------R1D--------------------------------
CMOS 1Dh - MCA - SLOT 2 ADAPTER CARD ID
----------R1D--------------------------------
CMOS 1Dh - AMI - First Hard Disk user defined: Number of Heads
----------R1D--------------------------------
CMOS 1Dh - AMSTRAD - mouse button 1 scancode/ASCII code
Size:	WORD
Desc:	specify the BIOS keycode for keyboard scancode 7Dh
Note:	default: FFFFh	- (no translation)
SeeAlso: INT 09,CMOS 1Bh"AMSTRAD",CMOS 1Fh"AMSTRAD"
----------R1D--------------------------------
CMOS 1Dh - Zenith Z-200 monitor - BOOT DRIVE SELECTION

Bitfields for Zenith Z-200 boot drive selection:
Bit(s)	Description	(Table C0023)
 6-5	(0xx0 0000)
	00 - MFM Monitor
	01 - First floppy drive (A:)
	10 - First fixed disk (C:)
	11 - First floppy drive (A:). If not there then First fixed disk (C:)
		(this is the default).
----------R1D--------------------------------
CMOS 1Dh - PHOENIX - LSB of Word to 82335 RC2 roll compare register
--------y-R1D--------------------------------
CMOS 1Dh - AWARD - MSB of password checksum (see byte 1Ch)
----------R1D--------------------------------
CMOS 1Dh - Quadtel HT 12 BIOS - first user def. drive: # of cylinders low byte
----------R1E--------------------------------
CMOS 1Eh - MCA - SLOT 2 ADAPTER CARD ID
----------R1E--------------------------------
CMOS 1Eh - AMI - First Hard Disk user defined: WPC-low
Desc:	Write Precompensation Cylinder, Low Byte, for first user-defined hard
	  disk
----------R1E--------------------------------
CMOS 1Eh - PHOENIX - MSB of Word to 82335 RC2 roll compare register
----------R1E--------------------------------
CMOS 1Eh - AWARD - 2nd Hard Disk user defined: # of Cylinders Low Byte
----------R1E--------------------------------
CMOS 1Eh - Quadtel HT 12 BIOS - FIRST USER DEFINED DRIVE

Bitfields for Quadtel HT-12 user-defined drive heads/cylinders:
Bit(s)	Description	(Table C0024)
 7-4	number of heads
 3-0	number of cylinders (MSB)
----------R1F--------------------------------
CMOS 1Fh - MCA - SLOT 3 ADAPTER CARD ID
----------R1F--------------------------------
CMOS 1Fh - AMI - First Hard Disk user defined: WPC-high
Desc:	Write Precompensation Cylinder, high byte, for first user-defined
	  hard disk
----------R1F20------------------------------
CMOS 1Fh-20h - AMSTRAD - mouse button 2 scancode/ASCII code
Size:	WORD
Desc:	specify the BIOS keycode for keyboard scancode 7Eh
Note:	default: FFFFh	- (no translation)
SeeAlso: INT 09,CMOS 1Dh"AMSTRAD"
----------R1F--------------------------------
CMOS 1Fh - AWARD - 2nd Hard Disk user defined (type 48): # of Cylinders High
----------R1F--------------------------------
CMOS 1Fh - Quadtel HT 12 BIOS - first user def. drive: WPC-low
Desc:	Write Precompensation Cylinder, low byte, for first user-defined
	  hard disk
----------R20--------------------------------
CMOS 20h - MCA - SLOT 3 ADAPTER CARD ID
----------R20--------------------------------
CMOS 20h - AMI - First Hard Disk user defined: Control Byte

Bitfields for AMI user-defined hard disk control byte:
Bit(s)	Description	(Table C0025)
 7-6	no retries (1)
 5	bad sector map at last cylinder+1
 4	unused (0)
 3	more than 8 heads
 2-0	unused (0)
----------R20--------------------------------
CMOS 20h - AMI WinBIOS - First Hard Disk user defined: Landing Zone, Low Byte
----------R20--------------------------------
CMOS 20h - PHOENIX - First user defined hard disk (type 48) Cylinders LSB
----------R20--------------------------------
CMOS 20h - AWARD - 2nd Hard Disk user defined (type 48): Number of Heads
----------R20--------------------------------
CMOS 20h - Quadtel HT 12 BIOS - FIRST USER DEFINED DRIVE
SeeAlso: CMOS 26h"Quadtel"

Bitfields for Quadtel landing zone/write-precompensation:
Bit(s)	Description	(Table C0026)
 7-4	landing zone MSB
 3-0	write precom. cyl. MSB
----------R21--------------------------------
CMOS 21h - MCA - Programmable Option Select configuration byte 2
----------R21--------------------------------
CMOS 21h - AMI - First Hard Disk user defined: Landing Zone, Low Byte
----------R21--------------------------------
CMOS 21h - AMI WinBIOS - First Hard Disk user defined: Landing Zone, High Byte
----------R21--------------------------------
CMOS 21h - AMSTRAD - MOUSE X SCALING FACTOR
Note:	default: 0Ah
----------R21--------------------------------
CMOS 21h - PHOENIX - First user defined hard disk (type 48) Cylinders MSB
----------R21--------------------------------
CMOS 21h - AWARD - 2nd Hard Disk user defined (type 48): Write Precomp Low Byte
----------R21--------------------------------
CMOS 21h - Quadtel HT 12 BIOS - first user def. drive: landing zone low byte
----------R22--------------------------------
CMOS 22h - MCA - Programmable Option Select configuration byte 3
----------R22--------------------------------
CMOS 22h - AMI - First Hard Disk user defined: Landing Zone, High Byte
----------R22--------------------------------
CMOS 22h - AMI WinBIOS - First Hard Disk user defined: # of Sectors per track
----------R22--------------------------------
CMOS 22h - AMSTRAD - MOUSE Y SCALING FACTOR
Note:	default: 0Ah
----------R22--------------------------------
CMOS 22h - PHOENIX - First user defined hard disk (type 48)	 of Heads
----------R22--------------------------------
CMOS 22h - AWARD - 2nd Hard Disk user defined (type 48): Write Precomp High Byte
----------R22--------------------------------
CMOS 22h - Quadtel HT 12 BIOS - first user def. drive: sectors per track
----------R23--------------------------------
CMOS 23h - MCA - Programmable Option Select configuration byte 4
----------R23--------------------------------
CMOS 23h - AMI - First Hard Disk user defined: # of Sectors per track
----------R23--------------------------------
CMOS 23h - AMI WinBIOS - Second Hard Disk user defined: # Cylinders, Low Byte
----------R23--------------------------------
CMOS 23h - AMSTRAD - INITIAL VDU MODE AND DRIVE COUNT
Note:	default: 20h

Bitfields for Amstrad initial VDU mode/drive count:
Bit(s)	Description	(Table C0027)
 7	enables extended serial flow control (NB this is buggy)
 6	set if two floppy drives installed
 5-4	(from Amstrad 1640 tech ref)
	00    Internal video adapter
	01    CGA card added; 40 x 25 mode
	10    CGA card added; 80 x 25 mode
	11    mono card added; 80 x 25 mode
----------R23--------------------------------
CMOS 23h - PHOENIX - First user defined hard disk (type 48) Write Precomp. LSB
----------R23--------------------------------
CMOS 23h - AWARD - 2nd Hard Disk user defined (type 48): Landing Zone Low Byte
----------R23--------------------------------
CMOS 23h - Quadtel HT 12 BIOS - second user def. drive: # of cylinders low byte
----------R24--------------------------------
CMOS 24h - MCA - Programmable Option Select configuration byte 5
----------R24--------------------------------
CMOS 24h - AMI - Second Hard Disk user defined: # Cylinders, Low Byte
----------R24--------------------------------
CMOS 24h - AMI WinBIOS - Second Hard Disk user defined: # Cylinders, High Byte
----------R24--------------------------------
CMOS 24h - AMSTRAD - INITIAL VDU CHARACTER ATTRIBUTE
Note: default: 7h
----------R24--------------------------------
CMOS 24h - PHOENIX - First user defined hard disk (type 48) Write Precomp. MSB
----------R24--------------------------------
CMOS 24h - AWARD - 2nd Hard Disk user defined (type 48): Landing Zone High Byte
----------R24--------------------------------
CMOS 24h - Quadtel HT 12 BIOS - SECOND USER DEFINED DRIVE
SeeAlso: CMOS 1Eh"Quadtel",#C0024
----------R25--------------------------------
CMOS 25h - AMI - Second Hard Disk user defined: # of Cylinders, High Byte
----------R25--------------------------------
CMOS 25h - AMI WinBIOS - Second Hard Disk user defined: Number of Heads
----------R25--------------------------------
CMOS 25h - AMSTRAD - size of RAM disk in 2K blocks
Note:	default: 0  - only used by the RAMDISK software supplied.
----------R25--------------------------------
CMOS 25h - PHOENIX - First user defined hard disk (type 48) Parking zone LSB
----------R25--------------------------------
CMOS 25h - AWARD - 2nd Hard Disk user defined (type 48): Sectors per Track
----------R25--------------------------------
CMOS 25h - Quadtel HT 12 BIOS - second user def. drive: WPC-low
Desc:	Write Precompensation Cylinder, low byte
----------R25--------------------------------
CMOS 25h - COMPAQ 386 - MACHINE CONFIGURATION
SeeAlso: MEM F000h:FFE0h

Bitfields for Compaq machine configuration:
Bit(s)	Description	(Table C0099)
 3	soft drive???
----------R26--------------------------------
CMOS 26h - AMI - Second Hard Disk user defined: Number of Heads
----------R26--------------------------------
CMOS 26h - AMI WinBIOS - Second Hard Disk user defined: WPC-low
Desc:	Write Precompensation Cylinder, Low Byte
----------R26--------------------------------
CMOS 26h - AMSTRAD - INITIAL SYSTEM UART SETUP BYTE
Note:	default: E3h - format as for Int 14h fn 0
----------R26--------------------------------
CMOS 26h - PHOENIX - First user defined hard disk (type 48) Parking zone MSB
----------R26--------------------------------
CMOS 26h - AWARD - 1st Hard Disk user defined (type 49): # Cylinders, Low Byte
----------R26--------------------------------
CMOS 26h - Quadtel HT 12 BIOS - SECOND USER DEFINED DRIVE
SeeAlso: CMOS 20h"Quadtel",#C0026
----------R27--------------------------------
CMOS 27h - AMI - Second Hard Disk user defined: WPC-low
Desc:	Write Precompensation Cylinder, Low Byte
----------R27--------------------------------
CMOS 27h - AMI WinBIOS - Second Hard Disk user defined: WPC-high
Desc:	Write Precompensation Cylinder, High Byte
----------R27--------------------------------
CMOS 27h - AMSTRAD - INITIAL EXTERNAL UART SETUP BYTE
Note:	default: E3h - format as for Int 14h fn 0
----------R27--------------------------------
CMOS 27h - PHOENIX - First user defined hard disk (type 48) Sectors per track
----------R27--------------------------------
CMOS 27h - AWARD - 1st Hard Disk user defined (type 49): # Cylinders, High Byte
----------R27--------------------------------
CMOS 27h - Quadtel HT 12 BIOS - SECOND USER DEF. DRIVE: landing zone low byte
----------R28--------------------------------
CMOS 28h - AMI - Second Hard Disk user defined: WPC-high
Desc:	Write Precompensation Cylinder, High Byte
----------R28--------------------------------
CMOS 28h - AMI WinBIOS - Second Hard Disk user defined: Landing Zone, Low Byte
----------R28--------------------------------
CMOS 28h - HP Vectra - checksum over bytes 29h-2Dh
----------R28--------------------------------
CMOS 28h - AWARD - 1st Hard Disk user defined (type 49): Number of Heads
----------R28--------------------------------
CMOS 28h - Quadtel HT 12 BIOS - second user def. drive: sectors per track
----------R283F------------------------------
CMOS 28h-3Fh - AMSTRAD - user applications default: zeroes
----------R29--------------------------------
CMOS 29h - AMI - Second Hard Disk user defined: Control Byte
Note:	80h if # of heads is equal or greater than 8
----------R29--------------------------------
CMOS 29h - AMI WinBIOS - Second Hard Disk user defined: Landing Zone, High Byte
----------R29--------------------------------
CMOS 29h - PHOENIX - LSB word to Intel 82335 CC0 compare register
----------R29--------------------------------
CMOS 29h - AWARD - 1st Hard Disk user defined (type 49): Write Precomp Low Byte
----------R29--------------------------------
CMOS 29h - HP Vectra - OFFICIALLY RESERVED "CMOS_HPCONFIG"

Bitfields for HP Vectra CMOS_HPCONFIG:
Bit(s)	Description	(Table C0028)
 7	include byte 2Ch in checksum (default = 0)
 6	select second ROM video adapter as primary (default = 0)
 5-1	reserved
 0	manufacturing test enabled
----------R2A--------------------------------
CMOS 2Ah - AMI - Second Hard Disk user defined: Landing Zone, Low Byte
----------R2A--------------------------------
CMOS 2Ah - AMI WinBIOS - Second Hard Disk user defined: # of Sectors per track
----------R2A--------------------------------
CMOS 2Ah - HP Vectra - OFFICIALLY RESERVED
----------R2A--------------------------------
CMOS 2Ah - PHOENIX - MSB word to Intel 82335 CC0 compare register
----------R2A--------------------------------
CMOS 2Ah - AWARD - 1st Hard Disk user defined (type 49): Write Precomp High
----------R2B--------------------------------
CMOS 2Bh - AMI - Second Hard Disk user defined: Landing Zone, High Byte
----------R2B--------------------------------
CMOS 2Bh - AMI WinBIOS - IDE and shadowing control

Bitfields for AMI WinBIOS IDE/shadowing control:
Bit(s)	Description	(Table C0029)
 7	LBA mode enabled
 6	IDE block mode enabled
 5	32-bit transfer enabled
 4	unused
 3	shadowing of DC00h enabled
 2	shadowing of D800h enabled
 1	shadowing of D400h enabled
 0	shadowing of D000h enabled
SeeAlso: #C0030
----------R2B--------------------------------
CMOS 2Bh - HP Vectra - OFFICIALLY RESERVED
----------R2B--------------------------------
CMOS 2Bh - PHOENIX - LSB word to Intel 82335 CC1 compare register
----------R2B--------------------------------
CMOS 2Bh - AWARD - 1st Hard Disk user defined (type 49): Landing Zone  Low Byte
----------R2C--------------------------------
CMOS 2Ch - AMI - Second Hard Disk user defined: # of Sectors per track
----------R2C--------------------------------
CMOS 2Ch - AMI WinBIOS - CACHE CONTROL

Bitfields for AMI WinBIOS cache control:
Bit(s)	Description	(Table C0030)
 7	external RAM cache enabled
 6	internal RAM cache enabled
 5	shadowing of E000h enabled
 4	shadowing of CC00h enabled
 3	shadowing of C800h enabled
 2	shadowing of C400h (video ROM) enabled
 1	shadowing of C000h (video ROM) enabled
 0	shadowing of system BIOS (F000h, 64K) enabled
SeeAlso: #C0029
----------R2C--------------------------------
CMOS 2Ch - HP Vectra - OFFICIALLY RESERVED
----------R2C--------------------------------
CMOS 2Ch - COMPAQ - NumLock CONTROL

Bitfields for Compaq NumLock control:
Bit(s)	Description	(Table C0031)
 6	0 - numlock OFF on boot, 1 - numlock ON at boot
----------R2C--------------------------------
CMOS 2Ch - PHOENIX - MSB word to Intel 82335 CC1 compare register
----------R2C--------------------------------
CMOS 2Ch - AWARD - 1st Hard Disk user defined (type 49): Landing Zone High Byte
----------R2D--------------------------------
CMOS 2Dh - AMI Hi-Flex BIOS - CONFIGURATION OPTIONS 

Bitfields for AMI Hi-Flex BIOS configuration options:
Bit(s)	Description	(Table C0032)
 7	Weitek Installed
 6	Floppy Drive Seek - turn off for fast boot
 5	Boot Order
	0 - Drive C:, then A:
	1 - Drive A:, then C:
 4	Boot Speed (0 - Low; 1 - High)
 3	External Cache Enable (1 = On)
 2	Internal Cache Enable (1 = On)
 1	Use Fast Gate A20 after boot (1 = On)
 0	Turbo Switch (1 = On)
----------R2D--------------------------------
CMOS 2Dh - AMI WinBIOS - flags

Bitfields for AMI WinBIOS flags:
Bit(s)	Description	(Table C0033)
 7	Weitek Installed
 6	bootsector virus protection enabled