[Techtoolslist] Slowing down a Fluke Z80 pod?

[Ian Eure]

David Gersic writes:

> 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.
>
Agreed.


>
>> 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.
>
Paul Swan does, and has a huge amount of repair/restore logs at
http://zzzaccaria.com/  -- I’ve emailed him before.

He made the tester I linked, which he uses for all his repairs, so I
don’t know if he’d be helpful in this case.  But a good guy to know
about if you’re working on Zaccaria boards.

>
>> 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.
>
It definitely doesn’t.  It has to run from the PCB’s clocks.