72 lines
1.1 KiB
NASM
72 lines
1.1 KiB
NASM
section .bss
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drives: equ 16
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; drive table entry
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struc drive
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.biosnum: resb 1
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.flag: resb 1
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.spc: resw 1
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.cylinders: resw 1
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.dpt: resb dpt_size
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endstruc
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; ptr into currently selected drive
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drive_ptr: resw 1
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drive_table: resb (drives * drive_size)
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section .text
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drives_init: int 0x11
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mov cl, 6
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shr ax, cl
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inc ax
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and ax, 3
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mov cx, ax
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mov bx, drive_table
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xor dx, dx
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mov [bx+drive.biosnum], dl
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; defaults if 13h,AH=8 fails (XT 360kb)
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les di, [0x1e * 4]
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mov cx, 0x2709 ; 40 cylinders, 9 sectors
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mov dh, 1 ; 2 heads
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; ask bios
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push bx
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mov ah, 8
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int 0x13
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pop bx
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; copy dpt
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push es
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push ds
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pop es
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pop ds
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push cx
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mov si, di
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lea di, [bx+drive.dpt]
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mov cx, 11
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rep movsb
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pop cx
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; restore ds
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push cs
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pop ds
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; get and save number of cylinders
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mov ax, cx
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xchg al, ah
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rol ah, 1
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rol ah, 1
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and ax, 0x03FF
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inc ax
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mov [bx+drive.cylinders], ax
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; save spt
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mov ax, cx
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and al, 0x3F
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mov [bx+drive.dpt+dpt.lastsector], al
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; multiply with heads and save sectors per cylinder
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inc dh
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mul dh ; ax = al * dh
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mov [bx+drive.spc], ax
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ret
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