| 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Functions for hard disk capacity calculations.
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| 3 |
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| 4 | ; Section containing code
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| 5 | SECTION .text
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| 6 |
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| 7 | ;--------------------------------------------------------------------
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| 8 | ; Calculates sector count from L-CHS values returned by INT 13h, AH=08h.
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| 9 | ;
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| 10 | ; HCapacity_GetSectorCountFromForeignAH08h:
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| 11 | ; HCapacity_GetSectorCountFromOurAH08h:
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| 12 | ; Parameters:
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| 13 | ; DL: Drive number
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| 14 | ; DS: RAMVARS segment
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| 15 | ; Returns:
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| 16 | ; DX:AX: Total sector count
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| 17 | ; BX: Zero
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| 18 | ; Corrupts registers:
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| 19 | ; CX
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| 20 | ;--------------------------------------------------------------------
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| 21 | ALIGN JUMP_ALIGN
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| 22 | HCapacity_GetSectorCountFromForeignAH08h:
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| 23 | mov ah, 08h ; Get Drive Parameters
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| 24 | call Int13h_CallPreviousInt13hHandler
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| 25 | jmp SHORT HCapacity_ConvertAH08hReturnValuesToSectorCount
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| 26 |
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| 27 | ALIGN JUMP_ALIGN
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| 28 | HCapacity_GetSectorCountFromOurAH08h:
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| 29 | push di
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| 30 | call AH8h_GetDriveParameters
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| 31 | pop di
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| 32 | ; Fall to HCapacity_ConvertAH08hReturnValuesToSectorCount
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| 33 |
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| 34 | ALIGN JUMP_ALIGN
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| 35 | HCapacity_ConvertAH08hReturnValuesToSectorCount:
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| 36 | call HAddress_ExtractLCHSFromBiosParams
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| 37 | xor ax, ax ; Zero AX
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| 38 | inc cx ; Max cylinder number to cylinder count
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| 39 | xchg al, bh ; AX=Max head number, BX=Sectors per track
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| 40 | inc ax ; AX=Head count
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| 41 | mul bx ; AX=Head count * Sectors per track
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| 42 | mul cx ; DX:AX = Total sector count
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| 43 | xor bx, bx ; Zero BX for 48-bit sector count
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| 44 | ret
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