MEM 0040h:000Eh - SEGMENT OF EXTENDED 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. DATA SEGMENT (PS/2IBM PS/2, any model, newer BIOSes) Size: WORD SeeAlso: MEM 0040h:000Eh"PARALLEL",INT 15/AH=C1h Format of Extended BIOS Data AreaA block of memory, typically the 1K at the top of conventional memory, which is used to store additional data for use by the BIOS which does not fit into the 256-byte data area at segment 0040h. (IBMInternational Busiuness MachinesInternational Busiuness Machines) A hardware, software and other service technology company founded in 1911.): Offset Size Description (Table M0001) 00h BYTE length of EBDA in kilobytes 01h 15 BYTEs reserved 17h BYTE number of entries in POSTsee Power-On Self-Test error log (0-5) 18h 5 WORDs POSTsee Power-On Self-Test error log (each word is a POSTsee Power-On Self-Test error number) 22h DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. Pointing Device DriverAn interface module between the device-independent portions of the operating system and an actual hardware device which converts device-independent requests into the actual sequence of device operations to perform the requested action. IO.SYS contains the standard, built-in MSDOS device drivers such as CON, COM1, AUX, PRN, etc. See also INT 21h Function 52h and INT 2Fh Function 0802h. 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 DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. Vector for INT 07h stored here during 80387 interrupt 34h DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. 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(Central Processing Unit) The microprocessor which executes programs on your computer. cache failed test bit 0: CPU(Central Processing Unit) The microprocessor which executes programs on your computer. cache disabled 69h-6Bh ??? 6Ch BYTE Fixed disk: (=FFh on ESDI(Enhanced Small Device Interface) A disk drive interface type which was briefly popular before IDE took over. An ESDI drive can transfer data between the drive and controller at 10, 15, or 20 megabits per second, which is faster than an MFM or RLL controller but slower than what is possible with an IDE or SCSI drive. See also IDE. systems) bits 7-4: Channel number 00-0Fh bits 3-0: DMAsee Direct Memory Access 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 DMAsee Direct Memory Access 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 DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. old INT 76h vector 78h BYTE hard disk DMAsee Direct Memory Access 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 5¼-inch instead of 3½-inch bit 0: drive 0 is 5¼-inch 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(Central Processing Unit) The microprocessor which executes programs on your computer. family ID (03h = 386, 04h = 486, etc.) (see INT 15/AH=C9h) EFh BYTE CPU(Central Processing Unit) The microprocessor which executes programs on your computer. 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(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. before calling user INT 18h at offset 11Dh 11Bh 2 BYTE ??? 11Dh DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. user INT 18h vector if 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. has re-hooked INT 18h 121h and up: ??? seen non-zero on Model 60 3F0h BYTE Fixed disk buffer (???) SeeAlso: #M0004 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 SeeAlso: #M0001,#M0003 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 SeeAlso: #M0001,#M0002 Format of Extended BIOS Data AreaA block of memory, typically the 1K at the top of conventional memory, which is used to store additional data for use by the BIOS which does not fit into the 256-byte data area at segment 0040h. (AMIAmerican Megatrends, Inc.(American Megatrends, Inc.) A hardware, software and firmware company founded in 1985. v1.00.12.AX1T): Offset Size Description (Table M0004) 00h BYTE length of XBDAsee Extended BIOS Data Area in kilobytes 01h 15 BYTEs reserved 17h BYTE number of entries in POSTsee Power-On Self-Test error log (0-10) 18h 10 BYTEs unused??? 22h DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. Pointing Device DriverAn interface module between the device-independent portions of the operating system and an actual hardware device which converts device-independent requests into the actual sequence of device operations to perform the requested action. IO.SYS contains the standard, built-in MSDOS device drivers such as CON, COM1, AUX, PRN, etc. See also INT 21h Function 52h and INT 2Fh Function 0802h. 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(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself. See also ESDI. drive 0 manufacturer/model string B8h 41 BYTEs AMIBIOS copyright string E1h unused??? 102h WORD ??? flags bit 15: ??? 108h WORD offset of IntelIDECfgTbl (IDE(Integrated Drive Electronics) A type of disk drive interface which essentially extends the PCIBM PC's expansion bus all the way to the drive and places the drive controller on the disk drive itself. See also ESDI. configuration settings) within segment F000h 10Ah 2 BYTEs ??? 10Ch DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. pointer to routine to call for language-specific error messages 110h WORD offset in segment F000h of end of currently-loaded optional 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. subsystems (language, APM, etc.) 112h WORD offset in segment F000h of end of area avaiable for loading optional 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. 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 POSTsee Power-On Self-Test error log 214h ??? SeeAlso: #M0001,#M0005 Format of Extended BIOS Data AreaA block of memory, typically the 1K at the top of conventional memory, which is used to store additional data for use by the BIOS which does not fit into the 256-byte data area at segment 0040h. (PhoenixBIOS 4.0): Offset Size Description (Table M0005) 00h BYTE length of XBDAsee Extended BIOS Data Area in kilobytes 01h 33 BYTEs reserved 22h DWORDDoubleword; four bytes. Commonly used to hold a 32-bit segment:offset or selector:offset address. Pointing Device DriverAn interface module between the device-independent portions of the operating system and an actual hardware device which converts device-independent requests into the actual sequence of device operations to perform the requested action. IO.SYS contains the standard, built-in MSDOS device drivers such as CON, COM1, AUX, PRN, etc. See also INT 21h Function 52h and INT 2Fh Function 0802h. 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 SeeAlso: #M0001,#M0004