Mini Dos machine

I am (was) currently working on a mini i86 DOS machine.

An old modified PC-XT board serve as a test platform for the homemade BIOS.

All IO’s – keyboard, VGA Display, floppy disk, RS232 will be handle by a propeller chip board.

To date,

INT10 (video) and
INT 16 (keyboard) are working.

I am currently working on INT13 (disk) function.

An image disk of DOS 3.1 will be on a SD flash drive connected to the propeller chip.

To date, with INT13 AH=02 (read); sector 0, side 0, track 0, I am able to load DOS boot sector from the propeller chip.

Some pictures:


Video at:

Extract of propeller keyboard micro-code:

PRI sendKey(request) | dataToSend

dataToSend := 0                        ‘ DATA to return to the 8088

if request == KEYB_AVAILABLE
if kb.gotkey
dataToSend := kb.keyNoRetrieve

if request == KEYB_GET_KEY
dataToSend :=  kb.getkey

outa[15..8] := dataToSend

outa[DATA_AVAILABLE_FOR_8088] := 1
waitcnt(Delay_on + cnt)                                    ‘ Wait a moment so the 8088 has time to read it

outa[8..15] := 0
outa[DATA_AVAILABLE_FOR_8088] := 0
waitcnt(Delay_off + cnt)

return 0

Extract of Mini DOS Machine BIOS:

; Auteur:   Alain Boudreault (VE2CUY)
; Date:    2010.01.10

ORG     0h

start: jmp  cold
COLD:   MOV     AX,40h
MOV     Word ptr DS:72h,0


include cpu_test.asm

JZ      CPU_OK


include init_8xxxChips.asm
include Get_MemSize.asm
include Install_int_vectors.asm
include Inst_Basic_Rom.asm

include Check_Devices.asm

2 Responses to Mini Dos machine

  1. kso says:

    Why don’t you release the project so we can all rebuilt this?
    If you are not willing to do so, please write it here because people are confused.

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