5/10/2021
`
`The BIOS Web: System BIOS [Extended BIOS Data Area]
`The Wayback Machine- http://web.archive.org/web/20061001225048/http:/www.matrix-bios.nl/system/ebda.htm|
`
`Extended BIOS Data Area
`
`Some BlOSesstore additional data in the last 1 KB of conventional memory.In general this socalled Extended BIOS Data Areawill be used to hold data for a mouse port, hard disk parameters and
`disk track buffers. The EBDA segmentis normally stored in the BIOS Data Area at 0040:000Eh,a location that wasoriginally used to store the port numberfor parallel port 4. This pointeris typically
`set to 9FCOh, representing a 1 KB memory areajust belowthe top of conventional memory. A few systems mayreserve 2 KB or even4 KB for the EBDA.
`
`[lyei=0ben=mes
`
`26h
`
`POSTerrorlog
`Mouse device driver far call
`
`Mouseflags 1
`
`it 7
`(Commandin progress; 0 = no, 1 = yes
`
`it 6
`Mouse sent a Resend byte (FAh)
`
`
`it 4
`Mouse sent anerror byte (FCh)
`i
`
`it 3
`Unexpected value received
`omthe’controller;
`i
`Index count; usedto retrieve up to 8 bytes
`successive bytes are storedstarting at offset28h:
`-
`27h
`
`evice driver far call
`flag
`lot used,or function unknown
`
`Ca
`
`
`NowedeaeSeepos
`
`Watchdog timer
`39h
`1 word
`Initial count value of the watchdog timer; 0 = watchdogtimer
`not active
`
`3Dh
`Hard disk 0 parametertable
`16 bytes
`The structure ofthis table is equalto the hard disk drive
`
`parametertable.
`4Dh
`Hard disk 1 parametertable
`16 bytes
`The structure ofthis table is equalto the hard disk drive
`
`parametertable.
`Primarily used for CPUs with on-chip cache: 486 CPUs and
`
`Not used
`Cachetest: 0 = test successful, 1 = test failed
`(CPU cache enable: 0 = enabled, 1 = disabled
`
`1 byte
`
` CPU stepping
`
`68h
`
`Cachecontrol
`Bit 7-2
`
`Bit 0
`
` IBM 386SLC.
`
`Values saved are identical to the values used by Int 16h,
`1 byte
`Keyboard repeatrate
`function 03h.
`6Fh
`Delay until keys repeat
`1 byte
`Values saved are identical to the values used byInt 16h,
`function 03h.
`N
`Numberof hard diskdrivesinstalled
`70h
`umberof drives as detected by POST: 0, 1 or 2
`byte
`DMAchannelfor hard disk drive
`71h
`Default: channel 5
`1 byte
`
`Hard disk interrupt status 1Fh = timeout has occurred 1 byte
`
`=3h
`Hard disk operation flags
`1 byte
`Bit 7
`1 = controller issued an operation complete interrupt
`Bit 6
`1 = controller has beenreset
`B50
`
`1
`
`(Old Int 76h vector pointer
`Hard disk DMAtype
`
`9h
`A)
`
`Hard disk: status of last operation
`Hard disk: timeout value
`
`1 dword
`
`byte
`
`1 byte
`{byte
`
`1 7
`
`Hard disk controller: return status words
`
`E7h
`
`Diskette drive type
`
`vy
`
`B words =|
`
`
`ECh
`Hard disk parameters loaded
`ial
`
`
`
`
`
`Bit
` The valuestored is the value returned byInt 15h, function C9hEEh CPUfamily ID|byte
`
`1 byte
`The value stored is the value returned byInt 15h, function C9h
`f
`1
`i]
`1
`|
`
`
`
`web.archive.org/web/20061001225048/http://www.matrix-bios.nl/system/ebda.html
`
`1/2
`
`Patent Owner, Bot M8 LLC - Ex. 2056, p. 1
`
`This byte is used as temporary storage for the DMA extended
`moderegister.
`Ti
`he value stored is the value returned byInt 13h, function 01h.
`The timeout value is set by POSTto indicate how long BIOS
`disk services should wait for the controller to indicate the
`operate has completed.
`ESDI - PS/2
`
`Patent Owner, Bot M8 LLC - Ex. 2056, p. 1
`
`

`

`The BIOS Web: System BIOS [Extended BIOS Data Area]
`5/10/2021
`
`[147h
`||Keyboard ID
`|[1. word
`|
`11h
`Non-BIOSInt 18h flag
`Bit 7-1
`Not used
`
`[raved
`
`
`
`Set to 1 before calling userInt 18h.
`[ser it har port
`
`web.archive.org/web/20061001225048/http://www.matrix-bios.nl/system/ebda.html
`
`2/2
`
`Patent Owner, Bot M8 LLC- Ex. 2056, p. 2
`
`Patent Owner, Bot M8 LLC - Ex. 2056, p. 2
`
`