[Coco] (very very slightly OT) 6800 emulator

Joel Ewy jcewy at swbell.net
Mon Apr 30 01:17:05 EDT 2007

Manney wrote:
> Joel Ewy wrote:
>>>> Interesting. Did you know the first 6809 emulator was written as a
>>>> 6800
>>>> program? It was made during the design of the 6809 at Motorola.
>>> Isn't that a bit backwards? :) But this question is coming from
>>> someone who isn't quite as in depth about 680x processors as he'd like
>>> to be. :)
>> It isn't backwards so much as forward, or ahead of its time.  :) How
>> better to test a microprocessor that doesn't exist yet but to emulate it
>> on one that does?
> Well, I thought that normally the 'host' processor had to be more
> powerful than the emulated processor to handle the emulation?
It does if you want to emulate it at full speed or better.  But
Motorola's purpose in emulating the 6809 on the 6800 wasn't to play cool
CoCo games from the past, er, from the future.  It was to test the
instruction set, and maybe to begin writing 6809 software (maybe
assemblers and such) before there were actual 6809 chips available. 
Yes, it would have been slower than the 6809, but it could have been
made to work just the 6809 would have.

> -M.
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