MEM 0040h:000Eh - SEGMENT OF EXTENDED BIOS DATA SEGMENT

MEM 0040h:000Eh - SEGMENT OF EXTENDED BIOS DATA SEGMENT (PS/2, newer BIOSes)


Size: WORD
SeeAlso: MEM 0040h:000Eh"PARALLEL",INT 15/AH=C1h

Format of Extended BIOS Data Area (IBM):
Offset Size Description (Table M0001)
 00h BYTE length of EBDA in kilobytes
 01h 15 BYTEs reserved
 17h BYTE number of entries in POST error log (0-5)
 18h  5 WORDs POST error log (each word is a POST error number)
 22h DWORD Pointing Device Driver entry point
 26h BYTE Pointing Device Flags 1 (see #M0002)
 27h BYTE Pointing Device Flags 2 (see #M0003)
 28h  8 BYTEs Pointing Device Auxiliary Device Data
 30h DWORD Vector for INT 07h stored here during 80387 interrupt
 34h DWORD Vector for INT 01h stored here during INT 07h emulation
 38h BYTE Scratchpad for 80287/80387 interrupt code
 39h WORD Timer3: Watchdog timer initial count
 3Bh BYTE ??? seen non-zero on Model 30
 3Ch BYTE ???
 3Dh 16 BYTEs Fixed Disk parameter table for drive 0 (for older machines which don't directly support the installed drive)
 4Dh 16 BYTEs Fixed Disk parameter table for drive 1 (for older machines which don't directly support the installed drive)
 5Dh-67h ???
 68h BYTE cache control
bits 7-2 unused (0)
bit 1: CPU cache failed test
bit 0: CPU cache disabled
 69h-6Bh ???
 6Ch BYTE Fixed disk: (=FFh on ESDI systems)
   bits 7-4: Channel number 00-0Fh
   bits 3-0: DMA arbitration level 00-0Eh
 6Dh BYTE ???
 6Eh WORD current typematic setting (see INT 16/AH=03h)
 70h BYTE number of attached hard drives
 71h BYTE hard disk 16-bit DMA channel
 72h BYTE interrupt status for hard disk controller (1Fh on timeout)
 73h BYTE hard disk operation flags
bit 7: controller issued operation-complete INT 76h
bit 6: controller has been reset
bits 5-0: unused (0)
 74h DWORD old INT 76h vector
 78h BYTE hard disk DMA type
typically 44h for reads and 4Ch for writes
 79h BYTE status of last hard disk operation
 7Ah BYTE hard disk timeout counter
 7Bh-7Dh
 7Eh  8 WORDs storage for hard disk controller status
 8Eh-E6h
 E7h BYTE floppy drive type
bit 7: drive(s) present
bits 6-2: unused (0)
bit 1: drive 1 is 5.25" instead of 3.5"
bit 0: drive 0 is 5.25"
 E8h  4 BYTEs ???
 ECh BYTE hard disk parameters flag
bit 7: parameters loaded into EBDA
bits 6-0: unused (0)
 EDh BYTE ???
 EEh BYTE CPU family ID (03h = 386, 04h = 486, etc.) (see INT 15/AH=C9h)
 EFh BYTE CPU stepping (see INT 15/AH=C9h)
 F0h 39 BYTEs ???
117h WORD keyboard ID (see INT 16/AH=0Ah)
(most commonly 41ABh)
119h BYTE ???
11Ah BYTE non-BIOS INT 18h flag
bits 7-1: unused (0)
bit 0: set by BIOS before calling user INT 18h at offset 11Dh
11Bh  2 BYTE ???
11Dh DWORD user INT 18h vector if BIOS has re-hooked INT 18h
121h and up: ??? seen non-zero on Model 60
3F0h BYTE Fixed disk buffer (???)




Bitfields for Pointing Device Flags 1:

Bit(s) Description (Table M0002)
 7 command in progress
 6 resend byte (FAh) received
 5 acknowledge byte (FEh) received
 4 error byte (FCh) received
 3 unexpected value received
 2-0 index count for auxiliary device data at 28h

Bitfields for Pointing Device Flags 2:
Bit(s) Description (Table M0003)
 7 device driver far call flag
 6-3 reserved
 2-0 package size (number of bytes received) - 1

Format of Extended BIOS Data Area (AMI v1.00.12.AX1T):
Offset Size Description (Table M0004)
 00h BYTE length of XBDA in kilobytes
 01h 15 BYTEs reserved
 17h BYTE number of entries in POST error log (0-10)
 18h 10 BYTEs unused???
 22h DWORD Pointing Device Driver entry point
 26h BYTE Pointing Device Flags 1 (see #M0002)
 27h BYTE Pointing Device Flags 2 (see #M0003)
 28h  8 BYTEs Pointing Device Auxiliary Device Data
 30h 13 BYTEs ???
 3Dh 16 BYTEs Fixed Disk parameter table for drive 0

 4Dh 16 BYTEs Fixed Disk parameter table for drive 1
 5Dh 16 BYTEs parameter table for drive 2???
 6Dh 16 BYTEs parameter table for drive 3???
 80h 56 BYTEs? IDE drive 0 manufacturer/model string
 B8h 41 BYTEs AMIBIOS copyright string
 E1h unused???
102h WORD ??? flags
bit 15: ???
108h WORD offset of IntelIDECfgTbl (IDE configuration settings) within segment F000h
10Ah  2 BYTEs ???
10Ch DWORD pointer to routine to call for language-specific error messages
110h WORD offset in segment F000h of end of currently-loaded optional BIOS subsystems (language, APM, etc.)
112h WORD offset in segment F000h of end of area avaiable for loading optional BIOS subsystems
1F0h BYTE APM status flags
1F1h  8 BYTEs APM power-state data for device classes 01h-06h
bits 0-3: current power state for devices 00h-03h in class
bits 7-4: current engaged state for devices 00h-03h in class
1F9h  4 BYTEs APM power-state data for device classes 01h-08h (four devices per class)
1FDh  3 BYTEs ???
200h 10 WORDs POST error log
214h ???

Format of Extended BIOS Data Area (PhoenixBIOS 4.0):
Offset Size Description (Table M0005)
 00h BYTE length of XBDA in kilobytes
 01h 33 BYTEs reserved
 22h DWORD Pointing Device Driver entry point
 26h BYTE Pointing Device Flags 1 (see #M0002)
 27h BYTE Pointing Device Flags 2 (see #M0003)
 28h  8 BYTEs Pointing Device Auxiliary Device Data