Showing how to use the Earliest known copy of 86-DOS, the antecedent to IBM PC-DOS. (MS-DOS)

Опубликовано: 19 Июнь 2026
на канале: tschak909

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This video gives an in-depth look at what is currently the oldest known copy of 86-DOS, the antecedent to #MSDOS aka #PCDOS, where we go through the process of moving from CP/M, translating Z80 to 8086 code, and assembling it. Since this DOS predates the IBM PC, it must be simulated via #SIMH as a Gazelle with a Cromemco 4FDC controller. #retrocomputing

86-DOS can be acquired here:
https://ia801209.us.archive.org/2/ite...

86-DOS manuals:
http://www.bitsavers.org/pdf/seattleC...
http://www.bitsavers.org/pdf/seattleC...

S-100 Computer information: http://s100computers.com/Hardware%20I...

SimH can be found here: https://github.com/simh/simh

The SIMH configuration file:
----------------------------
```
; $Id: 86dos 1968 2008-06-26 05:55:25Z hharte $
;
; SIMH/AltairZ80 Configuration File for SCP 86-DOS v1.0
; Copyright (c) 2008 Howard M. Harte
; www.86dos.org
;
;
set cpu 8086

; load SCP Monitor
load 86mon.bin 0
load 86mon.bin ff800

; Set serial port for SCP
set sio port=f6/0/0/0/0/F/0/T
set sio port=f7/0/2/0/1/F/0/F
set sio ansi

; Set up Cromemco 4FDC disk controller, with RDOS ROM disabled.
set cromfdc norom
set cromfdc en
set wd179x en
d cromfdc fdctype 4
att cromfdc0 86dos.img
att cromfdc1 cpmdata.img

echo
echo Press return to get monitor prompt, then type 'B' to boot
echo
go ffff0
```