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3 Commits
Author | SHA1 | Date |
---|---|---|
Juhani Krekelä | 199f632d53 | |
Juhani Krekelä | 1cbd918b56 | |
Juhani Krekelä | fea43699d7 |
2
Makefile
2
Makefile
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@ -2,7 +2,7 @@ DOSBOX=dosbox -conf dosbox-build.conf -exit
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ordos.img: BOOT.BIN IO.SYS ORDOS.SYS COMMAND.COM debug.com edlin.com exe2bin.exe link.exe masm.exe
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rm -f ordos.img
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mkfs.fat -C $@ -M 0xff 320
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mkfs.fat -C $@ 720
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rw -I 0x7c00 -i BOOT.BIN -o $@ -c 512
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mcopy -i $@ IO.SYS ::
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mcopy -i $@ ORDOS.SYS ::
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12
boot.asm
12
boot.asm
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@ -17,12 +17,12 @@ jmp code
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dw 512 ; Bytes per sector
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db 2 ; Sectors per cluster
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dw 1 ; Reserved sectors
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db 2 ; FATs
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fats db 2 ; FATs
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dw 112 ; Root directory entries
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dw 2*320 ; Total sectors
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db 0ffh ; Media descriptor
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dw 1 ; Sectors per fat
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sectorspertrack dw 8
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dw 2*720 ; Total sectors
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db 0f9h ; Media descriptor
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sectorsperfat dw 3 ; Sectors per fat
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sectorspertrack dw 9
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heads dw 2
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dd 0 ; Hidden sectors
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dd 0 ; Total sectors (large)
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@ -40,7 +40,7 @@ code:
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mov drivenumber, dl
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; TODO: Check we actually have the OS
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mov ax, 10
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mov ax, 14
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mov bx, 600h
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mov cx, 17 ; This is what PC-DOS 1.10's full size ends up at
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call loadsectors
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40
io.asm
40
io.asm
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@ -1,6 +1,8 @@
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; SPDX-License-Identifier: MIT
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; Copyright (c) 2021 Juhani 'nortti' Krekelä.
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debug equ 1
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iosegment equ 60h
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dossegment equ iosegment + 1*1024/16 ; DOS starts 1KiB after IO system
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@ -64,8 +66,10 @@ init:
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shl ax, cl
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; Memory size is passed in dx
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mov dx, ax
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if debug
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call hexprint16
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call newline
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endif
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; Disk table is passed in si
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mov si, offset iogroup:disks_table
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@ -94,9 +98,11 @@ init:
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test al, al
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jnz open_error
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if debug
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mov al, '+'
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mov ah, 0eh
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int 10h
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endif
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; Set random record field 0
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mov word ptr iogroup:command_fcb+33, 0
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@ -114,12 +120,14 @@ init:
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cmp al, 1
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jne read_error
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if debug
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mov ax, cx
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call hexprint16
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mov al, '.'
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mov ah, 0eh
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int 10h
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endif
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; Set up segments for command.com
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mov ds, bx
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@ -205,6 +213,7 @@ putch endp
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; OUT:
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; TODO: Document
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diskread proc far
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if debug
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push ax
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mov ax, 0e00h + 'r'
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int 10h
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@ -226,6 +235,7 @@ diskread proc far
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call hexprint16
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call newline
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pop ax
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endif
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; TODO: Everything except sregs can be trashed
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push es
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@ -266,13 +276,25 @@ diskread proc far
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dec di
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jz sector_read_fail
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reset_disk:
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if debug
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mov al, '"'
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mov ah, 0eh
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int 10h
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endif
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xor ax, ax
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int 13h
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pop cx
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pop ax
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jmp try_sector_read
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sector_read_fail:
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mov al, ah
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if debug
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call hexprint8;debg
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endif
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mov al, '?'
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mov ah, 0eh
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int 10h
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@ -532,7 +554,9 @@ error:
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mov ah, 0eh
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mov al, '!'
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int 10h
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if debug
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call far_caller
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endif
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hang:
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hlt
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@ -544,14 +568,15 @@ code ends
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constants segment
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sectorspertrack dw 8 ; TODO: Don't hardcode
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sectorspertrack dw 9 ; TODO: Don't hardcode
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heads dw 2 ; TODO: Don't hardcode
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disks_table:
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db 1 ; 1 drive, TODO: Don't hardcode
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db 0 ; Physical drive 0
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dw offset iogroup:parameters_320k
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;dw offset iogroup:parameters_320k
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dw offset iogroup:parameters_720k
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parameters_320k:
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dw 512 ; Sector size in bytes
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@ -561,6 +586,14 @@ parameters_320k:
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dw 112 ; Number of directory entries
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dw 320*2 ; Number of sectors
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parameters_720k:
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dw 512 ; Sector size in bytes
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db 2 ; Sectors per cluster
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dw 1 ; Number of reserved sectors
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db 2 ; Number of FATs
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dw 112 ; Number of directory entries
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dw 720*2 ; Number of sectors
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doubleticks_per_hour dw 32772 ; 1800B0h / 2 / 24
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ticks_per_minute dw 1092 ; 1800B0h / 24 / 60
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ticks_per_second dw 18 ; 1800B0h / 24 / 60 / 60
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@ -583,6 +616,8 @@ days_since_epoch: dw 0
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data ends
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code segment
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if debug
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hexprint16 proc
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xchg al, ah
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call hexprint8
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@ -672,6 +707,7 @@ logaddr proc
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ret
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logaddr endp
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endif
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code ends
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end
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