cmos.lst

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

 5	mouse enabled
 4	password checking (0 setup, 1 always)
 3	parity error check enabled
 2-1	boot order (00 = C:A:, 01 = A:C:)
 0	turbo switch enabled
----------R2D--------------------------------
CMOS 2Dh - HP Vectra - OFFICIALLY RESERVED
----------R2D--------------------------------
CMOS 2Dh - PHOENIX - ???
Note:	checks for values AAh or CCh
----------R2D--------------------------------
CMOS 2Dh - AWARD - 1st Hard Disk user defined (type 49): Sectors per Track
----------R2E--------------------------------
CMOS 2Eh - IBM - Standard CMOS Checksum, High Byte
----------R2F--------------------------------
CMOS 2Fh - IBM - Standard CMOS Checksum, Low Byte

 2Eh and 2Fh are as defined by the original IBM PC/AT specification and
 represent a byte-wise additive sum of the values in locations 10h-2Dh only,
 00h-0Fh and 30h-33h are not included. This definition is used by most
 clone manufacturers including AMI, Compaq, Tandon, NEC, and Zenith. The 
 IBM PS/2 line does not follow this standard with the range 19h-31h being 
 undefined.  On the original HP Vectra, this checksum only covers locations
 10h to 20h, with a separate checksum for bytes 29h-2Ch (see offset 28h).

----------R30--------------------------------
CMOS 30h - IBM - EXTENDED MEMORY IN KB (low byte)
SeeAlso: CMOS 17h"IBM",CMOS 31h
----------R31--------------------------------
CMOS 31h - IBM - EXTENDED MEMORY IN KB (high byte) 
 (this appears to mirror the value in bytes 17h-18h.) 
SeeAlso: CMOS 18h"IBM",CMOS 30h
----------R32--------------------------------
CMOS 32h - IBM - CENTURY BYTE (BCD value for the century - currently 19h)
SeeAlso: CMOS 7Fh
----------R32--------------------------------
CMOS 32h - IBM PS2 - CONFIGURATION CRC LOW BYTE
Desc:	CRC for range 10h-31h
SeeAlso: CMOS 33h"PS/2"
----------R33--------------------------------
CMOS 33h - IBM - INFORMATION FLAG

Bitfields for IBM information flag:
Bit(s)	Description	(Table C0034)
 7	128K ??? believe this indicates the presence of the special 128k
	  memory expansion board for the AT to boost the "stock" 512k
	  to 640k - all machines surveyed have this bit set)
 6-0	???
----------R33--------------------------------
CMOS 33h - IBM PS/2 - CONFIGURATION CRC HIGH BYTE (see entry for 32h)
SeeAlso: CMOS 32h"PS/2"
----------R33--------------------------------
CMOS 33h - PHOENIX - Bit 4 (000x 0000) bit 4 from Intel CPU register CR0
----------R33--------------------------------
CMOS 33h - AMI WinBIOS - INFORMATION FLAGS

Bitfields for AMI WinBIOS information flags:
Bit(s)	Description	(Table C0035)
 7	IBM-defined top 128K present
 6-4	CPU internal clock frequency
	000-011 = 25, 33, 40, 50 MHz
	100 = 60/66 MHz
	101 = 75 MHz
	110 = 80 MHz
	111 = 90/100 MHz
 2-1	CPU internal clock multiplier
	00-11 = 1,2,3,4
 0	FlashROM programming enabled (Ctrl-Home pressed at power on)
	Note: this location is not included in any CMOS checksum fields
----------R33--------------------------------
CMOS 33h - Quadtel HT12 BIOS 03.05.03 - INFORMATION FLAGS

Bitfields for Quadtel HT12 information flags:
Bit(s)	Description	(Table C0036)
 7	640K RAM present
 6	extension type (=CPU's Machine Status Word)
 1	print welcome message
----------R34--------------------------------
CMOS 34h - AMI - SHADOWING & BOOT PASSWORD
SeeAlso: CMOS 35h"AMI"

Bitfields for AMI shadowing control 1:
Bit(s)	Description	(Table C0037)
 7-6	password selection
	00b Disable
	10b Reserved
	01b Set
	11b Boot
 5	C8000h Shadow ROM (Bit 1 = On) 
 4	CC000h Shadow ROM (Bit 1 = On)
 3	D0000h Shadow ROM (Bit 1 = On)
 2	D4000h Shadow ROM (Bit 1 = On)
 1	D8000h Shadow ROM (Bit 1 = On)
 0	DC000h Shadow ROM (Bit 1 = On)
SeeAlso: #C0038
----------R34--------------------------------
CMOS 34h - AMI - EXTENDED MEMORY >16M (low byte)
Note:	this and the following byte contain the total extended memory in 64K
	  blocks
SeeAlso: CMOS 35h"AMI"
----------R34--------------------------------
CMOS 34h - (AMI WinBIOS) system-specific information (bits 3-1)
----------R343A------------------------------
CMOS 34h-3Ah - (AWARD) ??? unused ???  Defaults to all FFh's.
----------R35--------------------------------
CMOS 35h - AMI - EXTENDED MEMORY >16M (high byte)
Note:	this and the previous byte contain the total extended memory in 64K
	  blocks
SeeAlso: CMOS 34h"AMI"
----------R35--------------------------------
CMOS 35h - AMI - SHADOWING CONTROL 2
SeeAlso: CMOS 34"AMI"

Bitfields for AMI shadowing control 2:
Bit(s)	Description	(Table C0038)
 7	E0000h Shadow ROM (Bit 1 = On)
 6	E4000h Shadow ROM (Bit 1 = On)
 5	E8000h Shadow ROM (Bit 1 = On)
 4	EC000h Shadow ROM (Bit 1 = On)
 3	F0000h Shadow ROM (Bit 1 = On)
 2	C0000h Shadow ROM (Bit 1 = On)
 1	C4000h Shadow ROM (Bit 1 = On)
 0	reserved
SeeAlso: #C0037
----------R35--------------------------------
CMOS 35h - AMI WinBIOS - EXTENDED MEMORY SIZE IN 64K BLOCKS (low byte)
SeeAlso: CMOS 36h"AMI WinBIOS"
----------R35--------------------------------
CMOS 35h - PHOENIX - Second user defined hard disk (type 48) Cylinders LSB
Note:	used only when PS/2 style password is NOT in effect
----------R35--------------------------------
CMOS 35h - AMI 1990 Hyundai super-NB368S notebook

Bitfields for Hyundai configuration:
Bit(s)	Description	(Table C0039)
 3-1	shadowing
	000  shadow disabled
	011  video BIOS shadowed
	100  main BIOS shadowed
	111  both
 0	coprocessor enabled
----------R36--------------------------------
CMOS 36h - PHOENIX - Second user defined hard disk (type 48) Cylinders MSB
Note:	used only when PS/2 style password is NOT in effect.
----------R36--------------------------------
CMOS 36h - AWARD - IDE control

Bitfields for AWARD IDE control:
Bit(s)	Description	(Table C0040)
 6	IDE 32-bit transfer mode
----------R36--------------------------------
CMOS 36h - AMI - ???

Bitfields for AMI ???:
Bit(s)	Description	(Table C0041)
 1-0	???
 3-2	???
----------R36--------------------------------
CMOS 36h - AMI WinBIOS - EXTENDED MEMORY SIZE IN 64K BLOCKS (high byte)
----------R36--------------------------------
CMOS 36h - AMI 1990 Hyundai super-NB368S notebook - CPU/VIDEO CONFIGURATION

Bitfields for Hyundai CPU/video control:
Bit(s)	Description	(Table C0042)
 7	=1 LCD, 0 CRT at boot time
 6	=1 reversed, 0 normal video mode
 5	=1 external, 0 internal keyboard
 4-3	CPU speed
	00  high
	01  medium
	10  low
 2-1	harddisk vendor 1,2,3,4
 0	relocation enabled
----------R36--------------------------------
CMOS 36h - Quadtel HT12 BIOS 03.05.03 - EXTENDED MEMORY (low byte)
----------R37--------------------------------
CMOS 37h - IBM PS/2 - DATE CENTURY BYTE 
----------R37--------------------------------
CMOS 37h - PHOENIX - Second user defined hard disk (type 48) # of heads
       NOTE: used only when PS/2 style password is NOT in effect.
----------R37--------------------------------
CMOS 37h - AMI Hi-Flex BIOS - ???

Bitfields for AMI Hi-Flex BIOS location 37h:
Bit(s)	Description	(Table C0043)
 7	???
----------R37--------------------------------
CMOS 37h - AMI WinBIOS - SETUP COLORS, PASSWORD SEED

Bitfields for AMI WinBIOS setup colors and password seed:
Bit(s)	Description	(Table C0044)
 7-4	password seed
 3-0	WinBIOS/AMIBIOS setup color options
----------R37--------------------------------
CMOS 37h - Quadtel HT12 BIOS 03.05.03 - EXTENDED MEMORY (high byte)
--------y-R373A------------------------------
CMOS 37h-3Ah - AMI 1990 Hyundai super-NB368S notebook - PASSWORD
Desc:	encoded password, max 4 bytes.
----------R38--------------------------------
CMOS 38h - PHOENIX - Second user defined hard disk (type 48) Write Precomp. LSB
Note:	used only when PS/2 style password is NOT in effect.
--------y-R383D------------------------------
CMOS 38h-3Dh - AMI - Encrypted Password
--------y-R383F------------------------------
CMOS 38h-3Fh - ??? IBM PS/2 - Encrypted Password
Note:	Initialized to 00h in all bytes. Will accept from 1-7 scan codes. 
----------R39--------------------------------
CMOS 39h - PHOENIX - Second user defined hard disk (type 48) Write Precomp. MSB
Note:	used only when PS/2 style password is NOT in effect.
----------R3A--------------------------------
CMOS 3Ah - PHOENIX - Second user defined hard disk (type 48) Parking Zone LSB
Note:	used only when PS/2 style password is NOT in effect.
----------R3B--------------------------------
CMOS 3Bh - PHOENIX - Second user defined hard disk (type 48) Parking Zone MSB
Note:	used only when PS/2 style password is NOT in effect.
----------R3B--------------------------------
CMOS 3Bh - AWARD - CONFIGURATION BITS

Bitfields for AWARD configuration bits:
Bit(s)	Description	(Table C0045)
 4-7	Screen Colors Used in Setup (see #C0046)
 3-2	translation used for first disk
	00 normal, 01 LBA, 10 Large, 11 Auto
 1	??? Default = 1
 0	Enable External Cache

(Table C0046)
Values for AWARD setup colors:
 0000  Yellow/White on Blue (Default)
 0001  Magenta/White on Blue
 0010  Yellow/Black on Green
 0011  Yellow/Green on Cyan
 0100  Black/Yellow on Cyan
 0101  Brown/White on Cyan
 0110  White/Green on Red
 0111  White/White on Red
 1000  Green/White on Magenta
 1001  Yellow/Red on Magenta
 1010  Red/White on Grey
 1011  Yellow/White on Grey
 1100  Cyan/White on Grey
 1101  Cyan/Yellow on Black
 1110  White on Black (Monochrome)
 1111  Green/Red on Black
SeeAlso: #C0045
----------R3C--------------------------------
CMOS 3Ch - PHOENIX - Second user defined hard disk (type 48) Sectors per track
Note:	used only when PS/2 style password is NOT in effect.
----------R3C--------------------------------
CMOS 3Ch - AWARD - Boot Configuration Bits

Bitfields for AWARD boot configuration bits:
Bit(s)	Description	(Table C0047)
 7	disable virus warning on boot
 6,5	???
 4	Quick POST Enabled
 3,2	translation used for second disk
	00 normal, 01 LBA, 10 Large, 11 Auto
 1	Enable Turbo Switch Input
 0	0 = Boot from A, then C
	1 = Boot from C, then A
----------R3C--------------------------------
CMOS 3Ch - Quadtel HT12 BIOS 03.05.03 - TOTAL MEMORY (low byte)
SeeAlso: CMOS 3Dh"Quadtel"
----------R3D--------------------------------
CMOS 3Dh - AWARD - ???
----------R3D--------------------------------
CMOS 3Dh - Phoenix - ???
Note:	bit 3 = base memsize 512K/640K
----------R3D--------------------------------
CMOS 3Dh - Quadtel HT12 BIOS 03.05.03 - TOTAL MEMORY (high byte)
SeeAlso: CMOS 3Ch"Quadtel"
----------R3E--------------------------------
CMOS 3Eh - AMI - Extended CMOS Checksum, High Byte
Note:	this checksum covers locations 34h - 3Dh, but is not used by some
	  later AMI BIOSes
----------R3E--------------------------------
CMOS 3Eh - AWARD - BOOT CONFIGURATION BITS

Bitfields for AWARD boot configuration bits:
Bit(s)	Description	(Table C0048)
 7	Shadow Video BIOS at C000h
 6,5	???
 4	Swap Floppy Drive
 3	???
 2	Don't Halt on Diskette Errors at Boot
 1	Don't Halt on Keyboard Errors at Boot
 0	Never Halt for any error at Boot
----------R3E--------------------------------
CMOS 3Eh - Quadtel HT12 BIOS 03.05.03 - ???

Bitfields for Quadtel ???:
Bit(s)	Description	(Table C0049)
 2	system error occurred ?? (timer/RTC)
 0	=0 extended system configuration loaded
	=1 checksum error
----------R3E--------------------------------
CMOS 3Eh - Phoenix - SHADOWING CONTROL

Bitfields for Phoenix shadowing control:
Bit(s)	Description	(Table C0050)
 7	relocate enable
 1	shadow video enable
 0	shadow BIOS enable
----------R3F--------------------------------
CMOS 3Fh - AMI - Extended CMOS Checksum, Low Byte
Note:	this checksum covers locations 34h - 3Dh, but is not used by some
	  later AMI BIOSes
----------R3F--------------------------------
CMOS 3Fh - AWARD - ???
---------------------------------------------

 End of original 64 CMOS RAM bytes. Many modern chips now contain 128
 bytes and the IBM PS/2 has provision for 2k of "Expansion CMOS". 
 The AMI HI-FLEX description is below. If the chip does have only
 64 bytes, addresses will wrap so that requests for bytes 40h-7Fh will 
 return the same values as 00h-3Fh.

--------p-R40--------------------------------
CMOS 40h - AMI 1990 Hyundai super-NB368S notebook - POWER-SAVE CONFIGURATION

Bitfields for Hyundai power-save configuration:
Bit(s)	Description	(Table C0051)
 7	power save enabled
 6-0	HD power save wait, units of 1 minute (0-20)
----------R40--------------------------------
CMOS 40h - AWARD - Motherboard Chipset (SiS 85C501/85C502 shown)

Bitfields for AWARD motherboard chipset:
Bit(s)	Description	(Table C0052)
 7-1	???
 0	Automatic Configuration Enabled (Default: 1=enabled)
----------R4055------------------------------
CMOS 40h-55h - AMI WinBIOS - PCI BIOS setup data
----------R41--------------------------------
CMOS 41h - AMI - WAIT STATE CONFIGURATION