[99] | 1 | ; Project name : XTIDE Universal BIOS
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[3] | 2 | ; Description : Functions for accessing ATA information read with
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| 3 | ; IDENTIFY DEVICE command.
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| 4 |
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| 5 | ; Section containing code
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| 6 | SECTION .text
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| 7 |
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| 8 | ;--------------------------------------------------------------------
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[173] | 9 | ; LBA assist calculation:
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| 10 | ; this is how to fit a big drive into INT13's skimpy size requirements,
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| 11 | ; with a maximum of 8.4G available.
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[174] | 12 | ;
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| 13 | ; total LBAs (as obtained by words 60+61)
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[173] | 14 | ; divided by 63 (sectors per track) (save as value A)
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| 15 | ; Sub 1 from A
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[174] | 16 | ; divide A by 1024 + truncate.
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[173] | 17 | ; == total number of heads to use.
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| 18 | ; add 1
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| 19 | ; this value must be either 16, 32, 64, 128, or 256 (round up)
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| 20 | ; then take the value A above and divide by # of heads
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[174] | 21 | ; to get the # of cylinders to use.
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[173] | 22 | ;
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| 23 | ;
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| 24 | ; so a LBA28 drive will have 268,435,456 as maximum LBAs
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[174] | 25 | ;
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[173] | 26 | ; 10000000h / 63 = 410410h (total cylinders or tracks)
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| 27 | ; 410410h / 1024 = 1041h, which is way more than 256 heads, but 256 is max.
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| 28 | ; 410410h / 256 = 4104h cylinders
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| 29 | ;
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| 30 | ; there's a wealth of information at: http://www.mossywell.com/boot-sequence
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| 31 | ; they show a slightly different approach to LBA assist calulations, but
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| 32 | ; the method here provides compatibility with phoenix BIOS
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| 33 | ;
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| 34 | ; we're using the values from 60+61 here because we're topping out at 8.4G
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| 35 | ; anyway, so there's no need to use the 48bit LBA values.
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| 36 | ;
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[174] | 37 | ; AtaID_GetLbaAssistedCHStoDXAXBLBH:
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[173] | 38 | ; Parameters:
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| 39 | ; BX:DX:AX: Total number of sectors
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| 40 | ; Returns:
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| 41 | ; DX:AX: Number of cylinders
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| 42 | ; BH: Number of sectors per track (always 63)
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| 43 | ; BL: Number of heads (16, 32, 64, 128 or 255)
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| 44 | ; Corrupts registers:
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| 45 | ; CX
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| 46 | ;--------------------------------------------------------------------
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| 47 | AtaID_GetLbaAssistedCHStoDXAXBLBH:
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| 48 | push bp
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| 49 | push si
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| 50 |
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| 51 | ; Value A = Total sector count / 63
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| 52 | xor cx, cx
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| 53 | push cx ; Push zero for bits 48...63
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| 54 | push bx
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| 55 | push dx
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| 56 | push ax ; 64-bit sector count now in stack
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| 57 | mov cl, LBA_ASSIST_SPT
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| 58 | mov bp, sp ; SS:BP now points sector count
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| 59 | call Math_DivQWatSSBPbyCX ; Temporary value A now in stack
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| 60 |
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| 61 | ; BX = Number of heads = A / 1024
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| 62 | mov ax, [bp]
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| 63 | mov dx, [bp+2]
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| 64 | mov bx, [bp+4]
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| 65 | call Size_DivideSizeInBXDXAXby1024andIncrementMagnitudeInCX
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| 66 |
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| 67 | ; Heads must be 16, 32, 64, 128 or 256 (round up)
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| 68 | mov bx, 256 ; Max number of heads
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| 69 | test dx, dx ; 65536 or more heads?
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| 70 | jnz SHORT .GetNumberOfCylinders
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| 71 | mov cx, 128 ; Half BX for rounding up
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| 72 | .FindMostSignificantBitForHeadSize:
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| 73 | cmp ax, cx
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| 74 | jae SHORT .GetNumberOfCylinders
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| 75 | shr cx, 1
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| 76 | shr bx, 1 ; Halve number of heads
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| 77 | jmp SHORT .FindMostSignificantBitForHeadSize
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| 78 |
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| 79 | ; DX:AX = Number of cylinders = A / number of heads
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| 80 | .GetNumberOfCylinders:
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| 81 | mov cx, bx
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| 82 | call Math_DivQWatSSBPbyCX
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| 83 | mov ax, [bp]
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| 84 | mov dx, [bp+2] ; Cylinders now in DX:AX
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| 85 |
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| 86 | ; Return LBA assisted CHS
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| 87 | add sp, BYTE 8 ; Clean stack
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| 88 | sub bl, bh ; Limit heads to 255
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| 89 | mov bh, LBA_ASSIST_SPT
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| 90 | pop si
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| 91 | pop bp
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| 92 | ret
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| 93 |
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| 94 |
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| 95 | ;--------------------------------------------------------------------
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[169] | 96 | ; AtaID_GetPCHStoAXBLBHfromAtaInfoInESSI
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[3] | 97 | ; Parameters:
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| 98 | ; ES:SI: Ptr to 512-byte ATA information read from the drive
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| 99 | ; Returns:
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| 100 | ; AX: Number of user specified P-CHS cylinders
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[99] | 101 | ; BH: Number of user specified P-CHS sectors per track
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| 102 | ; BL: Number of user specified P-CHS heads
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[3] | 103 | ; Corrupts registers:
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| 104 | ; Nothing
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| 105 | ;--------------------------------------------------------------------
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[169] | 106 | AtaID_GetPCHStoAXBLBHfromAtaInfoInESSI:
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[3] | 107 | mov ax, [es:si+ATA1.wCylCnt] ; Cylinders (1...16383)
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[99] | 108 | mov bl, [es:si+ATA1.wHeadCnt] ; Heads (1...16)
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| 109 | mov bh, [es:si+ATA1.wSPT] ; Sectors per Track (1...63)
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[3] | 110 | ret
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| 111 |
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| 112 |
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| 113 | ;--------------------------------------------------------------------
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[165] | 114 | ; AtaID_GetTotalSectorCountToBXDXAXfromAtaInfoInESSI
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[3] | 115 | ; Parameters:
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| 116 | ; ES:SI: Ptr to 512-byte ATA information read from the drive
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| 117 | ; Returns:
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| 118 | ; BX:DX:AX: 48-bit sector count
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| 119 | ; Corrupts registers:
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| 120 | ; Nothing
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| 121 | ;--------------------------------------------------------------------
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[165] | 122 | AtaID_GetTotalSectorCountToBXDXAXfromAtaInfoInESSI:
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[173] | 123 | call Registers_ExchangeDSSIwithESDI ; ATA info now in DSDI
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[3] | 124 | xor bx, bx
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[173] | 125 | test BYTE [di+ATA1.wCaps+1], A1_wCaps_LBA>>8
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[99] | 126 | jz SHORT .GetChsSectorCount
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| 127 | ; Fall to .GetLbaSectorCount
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[3] | 128 |
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| 129 | ;--------------------------------------------------------------------
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[99] | 130 | ; .GetLbaSectorCount
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[173] | 131 | ; .GetLba28SectorCount
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| 132 | ; .GetChsSectorCount
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[3] | 133 | ; Parameters:
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| 134 | ; BX: Zero
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[99] | 135 | ; DS:SI: Ptr to 512-byte ATA information read from the drive
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[3] | 136 | ; Returns:
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| 137 | ; BX:DX:AX: 48-bit sector count
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| 138 | ; Corrupts registers:
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| 139 | ; Nothing
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| 140 | ;--------------------------------------------------------------------
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[99] | 141 | .GetLbaSectorCount:
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[173] | 142 | test BYTE [di+ATA6.wSetSup83+1], A6_wSetSup83_LBA48>>8
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[3] | 143 | jz SHORT .GetLba28SectorCount
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[173] | 144 | mov ax, [di+ATA6.qwLBACnt]
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| 145 | mov dx, [di+ATA6.qwLBACnt+2]
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| 146 | mov bx, [di+ATA6.qwLBACnt+4]
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| 147 | jmp SHORT .ExchangePtrAndReturn
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| 148 |
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[3] | 149 | .GetLba28SectorCount:
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[173] | 150 | mov ax, [di+ATA1.dwLBACnt]
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| 151 | mov dx, [di+ATA1.dwLBACnt+2]
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| 152 | jmp SHORT .ExchangePtrAndReturn
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[3] | 153 |
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[99] | 154 | .GetChsSectorCount:
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[173] | 155 | mov al, [di+ATA1.wSPT] ; AL=Sectors per track
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| 156 | mul BYTE [di+ATA1.wHeadCnt] ; AX=Sectors per track * number of heads
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| 157 | mul WORD [di+ATA1.wCylCnt] ; DX:AX=Sectors per track * number of heads * number of cylinders
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| 158 | .ExchangePtrAndReturn:
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| 159 | jmp Registers_ExchangeDSSIwithESDI
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