Check you clock signal on a scope, does the board have a two speed clock when access slow ram? Everything I have random read issues it's always a buggured clock.. it maybe good enough for the 2650 but not for the z80 On Sep 17, 2017 10:47 PM, "Rodger Boots" <rlboots2@gmail.com> wrote: It may be easier to speed up the board....cool the memory you're trying to test. Might just give you enough timing-wise to see where the hard failures are. On Sep 17, 2017 6:24 PM, "John Robertson" <jrr@flippers.com> wrote:

On 2017/09/17 4:23 PM, John Robertson wrote:

...

On 2017/09/17 9:38 AM, David Gersic wrote:

...

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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Silly question, but have you tried this adapter on a known-to-be-good 2650 board? Your UUT may be defective such that you get those results (ducking).

John :-#)#

Crap, you DID say KNOW TO BE WORKING 2650 board. !@#$.

Just ignore me.

John :-#(#

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