Mini i86 Dos machine

I am 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

18 réponses sur “Mini i86 Dos machine”

  1. Hey there!
    I’m just wondering how you connect the backs of your grid style circuit boards there. I have bought the same kind assuming I could easily connect the points with solder, but I have failed. And connecting them with wire to have a neat look like you have doesn’t work so well. Are you simply soldering wires to and from? I’d love a picture if you’d send me one! Thanks

  2. This is soooo cool. I really want to build a computer like this. I have built computers from parts but never from scratch. I was wondering if you could post more pictures like the back of the perfboard (i think thats what they’re called) and breadboard. And if you are really in a good mood, part numbers and descriptions of what they are. Thank You so much!

      1. Could you please provide me more info about the project? A schematic and the source code? I really need to experiment with it. My email can be found at the end of my website

  3. That’s incredible! That’s possible to have complete schemes and complete software? I want to rebuild your fantastic project! Can you send me it on an e-mail? I’ll use that only for personal and educational use. Thanks!

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