Accessing the CMOS (Cont.)
Bitfields for AMI WinBIOS cache control:
Bit(s) Description (Table C030)
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
See Also: #C029
----------R2C--------------------------------
CMOS 2Ch - HP Vectra - OFFICIALLY RESERVED
----------R2C--------------------------------
CMOS 2Ch - COMPAQ - NumLock CONTROL
Bitfields for Compaq NumLock control:
Bit(s) Description (Table C031)
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 C032)
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 C033)
7 Weitek Installed
6 bootsector virus protection enabled
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)
See Also: 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.)
See Also: CMOS 18h"IBM",CMOS 30h
----------R32--------------------------------
CMOS 32h - IBM - CENTURY BYTE (BCD value for the century - currently 19h)
----------R32--------------------------------
CMOS 32h - IBM PS2 - CONFIGURATION CRC LOW BYTE
Desc: CRC for range 10h-31h
See Also: CMOS 33h"PS/2"
----------R33--------------------------------
CMOS 33h - IBM - INFORMATION FLAG
Bitfields for IBM information flag:
Bit(s) Description (Table C034)
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)
See Also: 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 C035)
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 C036)
7 640K RAM present
6 extension type (=CPU's Machine Status Word)
1 print welcome message
----------R34--------------------------------
CMOS 34h - AMI - SHADOWING & BOOT PASSWORD
See Also: CMOS 35h"AMI"
Bitfields for AMI shadowing control 1:
Bit(s) Description (Table C037)
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)
See Also: #C038
----------R34--------------------------------
CMOS 34h - AMI - EXTENDED MEMORY >16M (low byte)
Note: this and the following byte contain the total extended memory in 64K
blocks
See Also: 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
See Also: CMOS 34h"AMI"
----------R35--------------------------------
CMOS 35h - AMI - SHADOWING CONTROL 2
See Also: CMOS 34"AMI"
Bitfields for AMI shadowing control 2:
Bit(s) Description (Table C038)
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
See Also: #C037
----------R35--------------------------------
CMOS 35h - AMI WinBIOS - EXTENDED MEMORY SIZE IN 64K BLOCKS (low byte)
See Also: 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 C039)
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 C040)
6 IDE 32-bit transfer mode
----------R36--------------------------------
CMOS 36h - AMI - ???
Bitfields for AMI ???:
Bit(s) Description (Table C041)
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 C042)
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 C043)
7 ???
----------R37--------------------------------
CMOS 37h - AMI WinBIOS - SETUP COLORS, PASSWORD SEED
Bitfields for AMI WinBIOS setup colors and password seed:
Bit(s) Description (Table C044)
7-4 password seed
3-0 WinBIOS/AMIBIOS setup color options
----------R37--------------------------------
CMOS 37h - Quadtel HT12 BIOS 03.05.03 - EXTENDED MEMORY (high byte)
----------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.
----------R383D------------------------------
CMOS 38h-3Dh - AMI - Encrypted Password
----------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