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‎.github/workflows/main.yml‎

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name: Build OBJ file
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on:
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push:
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branches: [ main ]
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pull_request:
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branches: [ main ]
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workflow_dispatch:
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jobs:
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build:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v2
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- uses: karcherm/action-install-jw@v1.0
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with:
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jwasm: true
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- name: Assemble the patch
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run: jwasm -Zm -Fo274x-211.obj 274x-211.asm
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- uses: actions/upload-artifact@v2
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with:
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name: scsi_edd
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path: |
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274x-211.obj
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bios16k.map

‎.gitignore‎

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*.obj
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*.lst
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*.bin

‎274x-211.asm‎

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; Patch for Adaptec's 274x BIOS, Version 2.11 to add (rudimentary) EDD support.
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; SHA1 of expected input file: A0EC9AFE433549BB384E76A4167C2CB14BFE3FDA
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; Copyright (C) 2021 Michael Karcher (the patch, not the original BIOS!)
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; This patch may be used and distributed according to the MIT License.
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.286
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BIOSFrame STRUC
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we_dont_care_1 db 4 dup (?)
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VDSFlags db ?
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we_dont_care_2 db 11 dup (?)
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CDBlen db ?
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we_dont_care_3 db 7 dup (?)
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CDBdata db 12 dup (?)
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we_dont_care_4 db 4 dup (?)
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TransferLenLow dw ?
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TransferLenHigh dw ?
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we_dont_care_5 db 8 dup (?)
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BIOSFlags dw ?
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we_dont_care_6 db 6 dup (?)
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CallerAX dw ?
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CallerBX dw ?
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CallerCX dw ?
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CallerDX dw ?
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CallerSI dw ?
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CallerDI dw ?
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CallerDS dw ?
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CallerES dw ?
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BIOSFrame ENDS
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IsNoData = 8 ; Flag for execution unit that this is a "no data" command
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BF_IgnoreSeek = 80h
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MAIN SEGMENT
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assume cs:MAIN
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org 0BF4h
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ResetLocalState LABEL NEAR
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org 0C28h
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SetTarget LABEL NEAR
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org 0DE1h
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ExecuteCommand LABEL NEAR
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org 0E9Fh
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SetDataAddress LABEL NEAR
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org 13ECh
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Func_Unsupported LABEL NEAR
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org 13EEh
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I13FinishWithAH LABEL NEAR
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org 16F4h
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Func09_AlwaysOK LABEL NEAR
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org 1224h + 12h * 2
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; remap functions 12..14 ("always OK") to function 09 ("always OK")
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; this frees up 13E4..13E8
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dw OFFSET Func09_AlwaysOK
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dw OFFSET Func09_AlwaysOK
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dw OFFSET Func09_AlwaysOK
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org 1224h
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Int13_Dispatch LABEL WORD
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org 13BCh
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mov al, BYTE PTR [bp+CallerAX+1] ; originaly whole word to AX
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;mov bx, [bp+CallerBX] ; superflous, BX is already set
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mov cx, [bp+CallerCX]
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mov dx, [bp+CallerDX]
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push 40h
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pop ds
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cbw
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mov di, ax
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shl di, 1
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cmp al, 15h
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ja short MaybeI13E
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mov ax, [bp+CallerAX]
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jmp cs:[di + Int13_Dispatch]
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MaybeI13E:
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sub al, 41h
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cmp al, 7
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ja Func_Unsupported
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mov es, [bp+CallerDS]
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jmp cs:[di - 41h*2 + Int13E_Dispatch]
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org 0B4Bh
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Int13E_Dispatch LABEL WORD
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dw OFFSET I13E_checkpresence ; 41h
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dw OFFSET I13E_read ; 42h
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dw OFFSET I13E_write ; 43h
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dw OFFSET I13E_verify ; 44h
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dw OFFSET Func_Unsupported ; 45h (lock/unlock)
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dw OFFSET Func_Unsupported ; 46h (eject)
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dw OFFSET I13E_seek ; 47h
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dw OFFSET I13E_params ; 48h
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I13E_checkpresence:
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mov [bp+CallerBX], 0AA55h ; extensions present
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mov byte ptr [bp+CallerAX + 1], 01h ; version 1.x
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mov [bp+CallerCX], 1 ; support LBA disk calls only
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jmp Func09_AlwaysOK
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I13E_params:
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mov di, si
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mov ax, 1Ah
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cmp es:[word ptr di], ax
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jnb go_on
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jmp Func_Unsupported
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go_on:
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stosw
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mov ax, 1 ; No 64K DMA limit, no CHS info
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stosw
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dec ax
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mov cx, 6
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rep stosw ; clear CHS fields (not reporting them)
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push es
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push di
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call ResetLocalState
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call SetTarget
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mov [bp+CDBdata], 25h ; SCSI read capacity
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mov [bp+CDBlen], 0Ah
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mov [bp+TransferLenLow], 8
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mov [bp+TransferLenHigh], 0
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and [bp+VDSFlags], not IsNoData
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pop bx ; address of LBA count.
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; if the command succeeds, the low 32 bits are set to the
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; capacity of the drive (-1), the high 32 bits are the sector size.
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; it's big endian, though :(
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push bx
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call SetDataAddress
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call ExecuteCommand
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pop di
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pop es
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push ax
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mov ax, es:[di]
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xchg ah, al
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xchg ax, es:[di+2]
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xchg ah, al
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add ax, 1 ; from max_lba to sector count
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mov es:[di], ax
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adc es:[word ptr di+2], 0
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add di, 4
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xor ax, ax
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stosw ; high 32 bit of max LBA
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stosw
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mov ax, 200h ; sector size
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stosw
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pop ax
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jmp I13FinishWithAH
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org 184Ah
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I13E_common:
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sbb dx,dx
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call ResetLocalState
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or [bp+VDSFlags], ch
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mov [bp+CDBdata], cl
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mov [bp+CDBlen], 0Ah
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mov ax, es:[si+2]
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and dx, ax
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xchg dh, dl
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mov word ptr [bp+CDBdata + 7], dx ; length to target
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add ax, ax
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mov word ptr [bp+TransferLenLow + 1], ax ; transfer length
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; set LBA (bswapping it)
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mov ax, es:[si+8]
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xchg ah, al
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mov word ptr [bp+CDBdata + 4], ax
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mov ax, es:[si+10]
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xchg ah, al
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mov word ptr [bp+CDBdata + 2], ax
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test [bp+VDSFlags], IsNoData
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jnz no_data
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les bx, es:[si+4]
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call SetDataAddress
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no_data:
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call ExecuteCommand
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cmp ah, 1 ; unsupported command
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jne usual_case
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test [bp+VDSFlags], IsNoData
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jz usual_case
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return_ok:
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mov ah, 0 ; non-data command: verify or seek; deemed optional
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; remap "unsupported" to OK
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usual_case:
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jmp I13FinishWithAH
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I13E_read:
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mov cx, 0028h
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stc
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jmp I13E_common
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I13E_write:
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mov cx, 002Ah
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stc
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jmp I13E_common
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I13E_verify:
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mov cx, 082Fh
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stc
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jmp I13E_common
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I13E_seek:
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test byte ptr [bp+BIOSFlags], BF_IgnoreSeek ; TEST always clears CF
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jnz return_ok
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mov cx, 082Bh
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jmp I13E_common
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org 18D8h
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db "EDD 1.0"
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MAIN ENDS
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END

‎LICENSE‎

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MIT License
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Copyright (c) 2021 Michael Karcher
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

‎README.md‎

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Int13 Extension support for Adaptec BIOSes
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==========================================
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How to use it
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-------------
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This repository contains patches for Adaptec SCSI BIOSes (currently only the 2740, more to come) to support the Phoenix/Microsoft Int13 extensions used to access hard disks above 8GB in LBA mode. To avoid potential copyright problems, this repository does not contain the actual Adaptec BIOSes. Instead, this repository contains an assembler source code file that generates an object file that contains only the locations that need to be overwritten to add Int 13 extension support to the respective BIOS images.
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To apply the patch, you need the assembled form of the patch, which can be generated using MASM or a compatible assembler like Borland's TASM or JWASM. This patch has been tested to assemble correctly on both TASM and JWASM, even though TASM produces a different output because TASM defaults to single-pass mode and the patch contains a non-annotated short forward jump. Both assembled versions are functionally identical. You can also just download the latest GitHub release which includes an assembled object file.
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To apply an object file as patch, my tool [omfpatch|https://github.com/karcherm/omfpatch] can be used. [Release 1.1|https://github.com/karcherm/omfpatch/releases/tag/v1.1] is known to work with this patch. You can choose to download either the DOS or the Win32 version of omfpatch depending on the system you want to use to apply the patch. The latest 274x BIOS (2.11) seems to not be available for download from the Adaptec / MicroSemi. Their page has version 2.10. This patch *does not apply to version 2.10*. You can obtain the ROM image by reading it from an controller that has the latest version. The ROM chip is an OTP chip labelled `549306-00 D BIOS 7D00 (c) 1993`.
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You can run `omfpatch 274x-211.bin bios16k.map 274x-211.obj` to create a patched BIOS image.
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The patched BIOS identifies itself as "2.11 EDD 1.0" instead of just "2.11 Release" to indicate the *extended disk drive* specification.
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Disclaimer
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----------
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If you patch your BIOS and something goes wrong, the computer may become unbootable. It is recommended that you have a way to recover your BIOS, like an external flasher connected to a different computer. Make a backup of your BIOS before your install a patched BIOS.

‎bios16k.map‎

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MAIN 0 0 0x3FFF
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!CHKSUM SUM8 0 0x3FFF 0x3FFF

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