Testing 256kz without a 68k processor

[christopher.mallery]

I have a Z-2 booting into Z-80 Cromix with a 256kz board.  I also have another "bad" 256kz board.  However, I cannot figure out how to test the 256kz board without using 68kmemt.com, which obviously requires a 68k processor.  Is there any way to hunt down the what is wrong with the bad 256kz using only a Z-80?

Thanks,

Chris

[David Roberts]

According to the 256kz manual, in a Z80 system the 256kz board appears as four (4) banks of 64K memory. The problem I forsee is being able to run a memory test program in a 64KB page that is (in itself) potentially faulty. Let me check the manual again and see if it is possible to run half of the memory board at a time...

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[David Roberts]

I can find the schematics for the 1024kz but not the 256kz...

On Thu, 27 Feb 2025, 05:00 christopher.mallery, <christoph...@gmail.com> wrote:

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[Mike Arnold]

Back in the 80s I wrote the attached test program. It runs under CDOS and tests using bank switching. I have not run it for years but you are welcome to try it. The crotst.xxx file is the assembled .com so you will have to rename it (attachment restrictions).

[Mike Arnold]

Just looked at the code and the above instruction is completely wrong. You run it under Z80 Cromix and it tests the memory bank that the user task is running in. I have a vague memory of writing something that switched banks but don't know where that is.

[Peter Higgins]

Schematic for the 256KZ attached.