[Techtoolslist] Slowing down a Fluke Z80 pod?

[David Gersic]

On Sunday, September 17, 2017 12:24:07 PM Ian Eure wrote:
> 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.

Hm. So the adapter ports CLOCK straight across, from Z80 pin 6 so 2650 pin 38. 
The Z80, being capable of running at faster clock speeds, should be perfectly 
happy to run slower.


> 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.

The old Fluke article seems like they were trying to match the timings, or at 
least get close enough. Maybe they were good enough for whatever it was they 
were testing when the article was written.

I don't know anybody else that works on Zaccaria boards, so no, haven't got 
anybody else that can confirm or deny that this works at all.


> 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.

Right now, I'm testing on boards that I know to be good. I could try swapping 
in a slower crystal to see what happens, good or bad. But if the pod runs at 
UUT clock speed, I'm thinking that wouldn't be likely to make a difference.


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

Yes, I've seen that too.