Perverted DOS idea

From: Hans Franke <>
Date: Thu Jun 8 10:25:00 2000

> I had a perverted idea of building a DOS emulator on a C64 -- i.e., have
> the C64 emulate the 8086 in software, either in real time or some sort of
> JIT compilation method.


> How little memory could you run something like, say, DOS 3.3 in? All I
> would be supporting is a basic command set like COMMAND.COM, EDLIN, DEBUG,
> maybe XCOPY, etc. And are the INTs documented anywhere?

If you'd like to boot DOS 2.11 (my recomendation) 128 K is sufficient
for DOS and most tools. It should be possible to strip it down to run
in as little as ~96 k, but below 64 K not even a complete boot is possible.

DOS 1.X is able to run in 64 K, although it will be hard to find programs
still able to run - after the introduction of DOS 2.0 everybody switched
for the new file I/O (Unix style, without FCBs).

CP/M 86 may be an alternativ way to go - way faster boot :)

Also, based on my experiance of a 8080 emulator I did on the KIM in 1979,
it will be hard to get a decent performance... I think the effective
speed on a C64 will be something like or below a 0.1 MHz 8086 (my 8080
emulation archived an equivalent of a 0.10-0.25 MHz 8080), depending on
the instruction mix of course

Say, wouldn't a Software CP/M system more aprobiate for a first step ?


VCF Europa 2.0 am 28./29. April 2001 in Muenchen
Received on Thu Jun 08 2000 - 10:25:00 BST

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