[Techtoolslist] Slowing down a Fluke Z80 pod?

[Ian Eure]

That’s not really how it works.  The CPU in the pod is driven by the
clock on the PCB.  If the pod CPU was running at a different clock
speed, nothing would work at all.

Based on the article, it sounds like perhaps the adapter just doesn’t
match the timings of the original CPU to support anything other than
individual reads, or perhaps there’s an issue with your adapter.  I’d
see if anyone else has used a similar setup and see what results they got.

If you wanted to slow things down in the hopes of improving marginal
timings, you’d need to alter the clock on the PCB, either by
substituting a slowre crystal or by replacing the clock that controls
the CPU and bus accesses with a slower signal.  Either option almost
certainly guarantees that the video hardware won’t work, and may mask
other problems going on with the board.

Are you aware of Paul Swan’s 2650 tester?  That might be another
option worth looking into.
http://www.paulswan.me/arcade/ArduinoMegaICT.htm

David Gersic writes:

> This is going to seem like a strange thing to want, but is it possible to slow 
> down a Z80 pod?
>
> I have a 9010 and the Z80 pod for it. As far as I know, both are working fine. 
> I don't have anything with a Z80 in it to test to prove that.
>
> What I picked these up for is to use with a Signetics 2650 adapter 
> (http://www.arcades.plus.com/s2650_fluke_adapter.htm) on Zaccaria boards. It 
> seems like this should work, but in practice it's very unreliable.
>
> Test reading data from ROM on a known working board, sometimes I get correct 
> data, most of the time I get random garbage. If I read a byte from the same 
> address 10 times, maybe one time will be correct.
>
> Test RAM, it'll go a few bytes in to the test, then "fail". If I loop on that, 
> it'll eventually pass, then fail a byte or two later. This seems to be 
> essentially the same symptom as displayed by the ROM reading test.
>
> The adapter board is based on the old Fluke "Troubleshooter" article from 
> 1983. As far as I can see, the board is doing what it's supposed to do, moving 
> signals from the Z80 to where the 2650 expects them to be.
>
> So what I'm thinking is that the Z80, running at a faster clock speed than the 
> 2650, is just over-running what a board designed for a slower processor can 
> deliver. Is it possible to slow down the clock speed on the Z80 pod?
>
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