semi-homemade micro

[Gooijen, Henk]

Allison wrote:

> Everyone has done the PC emulating whatever.  Why not take a 
> single chip micro and use that to emulate another micro as 
> hardware?  Same idea maybe slow but for a lot of things speed 
> is not the whole world.
> I did it on paper for PDP8 and it was possible using an 11mhz 
> 8049 to come within 1/10 the speed of a real 8.  I guess a 
> 36bit machine could be done as well (though really slow.).  
> Also a front pannel could be programmed into it as well 
> (maybe a speed hit).  Any cpu that gets an instruction from 
> memory and then executes it can be emulated that way. 

1/10 the speed of a real PDP8?  Really? That is fast indeed!
My emulation of a PDP8, running on a 68B09 (at 2 MHz) gets to
approx 1/60 of the real thing. I measured that by running some
diagnostics. The diag says "bell rings after approx 5 seconds),
and timed how long it took on my 68B09...
I am sure that when I remove the front panel code things run
faster. The front panel requires time to update. But running
the emulation without the front panel is no fun.

- Henk, PA8PDP.

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