| 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 | ; DS:DI: Ptr to DPT (HCapacity_GetSectorCountFromOurAH08h) |
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| 16 | ; Returns: |
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| 17 | ; DX:AX: Total sector count |
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| 18 | ; BX: Zero |
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| 19 | ; Corrupts registers: |
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| 20 | ; CX |
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| 21 | ;-------------------------------------------------------------------- |
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| 22 | ALIGN JUMP_ALIGN |
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| 23 | HCapacity_GetSectorCountFromForeignAH08h: |
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| 24 | mov ah, GET_DRIVE_PARAMETERS |
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| 25 | call Int13h_CallPreviousInt13hHandler |
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| 26 | jmp SHORT ConvertAH08hReturnValuesToSectorCount |
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| 27 | |
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| 28 | ALIGN JUMP_ALIGN |
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| 29 | HCapacity_GetSectorCountFromOurAH08h: |
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| 30 | call AH8h_GetDriveParameters |
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| 31 | ; Fall to ConvertAH08hReturnValuesToSectorCount |
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| 32 | |
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| 33 | ConvertAH08hReturnValuesToSectorCount: |
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| 34 | call HAddress_ExtractLCHSFromBiosParams |
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| 35 | xor ax, ax ; Zero AX |
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| 36 | inc cx ; Max cylinder number to cylinder count |
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| 37 | xchg al, bh ; AX=Max head number, BX=Sectors per track |
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| 38 | inc ax ; AX=Head count |
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| 39 | mul bx ; AX=Head count * Sectors per track |
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| 40 | mul cx ; DX:AX = Total sector count |
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| 41 | xor bx, bx ; Zero BX for 48-bit sector count (and clear CF) |
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| 42 | ret |
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