Re: Apple 1 CFFA1 AND FORTH +

[David Schmenk <dschmenk@gmail.com>]

On Nov 2, 4:03 am, mwillegal <m...@willegal.net> wrote:
> DRAM refresh suspends the CPU clock, so should have no effect on reads
> or writes on a real Apple 1, Obtronix or Mimeo.
> I'm heavily engaged in another project at this time, but I'll try this
> Forth port on a Mimeo, as soon as I get a chance.
> In the meantime, a while back, I have put up a page with a memory test
> that could be used to test the memory on any of these systems.
>
> http://www.willegal.net/appleii/6502mem.htm
>
> Regards,
> Mike Willegal
>

HI Mike-

I did use your memory test on my Obtronix.  It passed (actually it did
fail once, but ran for a day afterward).  However, I wouldn't put too
much faith in the test.  It checks to see if the value written is the
one read back, but there aren't any checks for secondary effects such
as other memory locations being affected by the one being tested (at
least that I could find).  I'm not saying that the refresh is
definitely the culprit.  I have no real diagnostic tools so I'm just
speculating as I can't think of any other differences in the way the
CPU, memory, and code interact at this point.  Rich and I went back
and forth (ha) over the best way to track down the failure.  He wanted
me to probe the address the CPU was at after it locked up and I wanted
to run the trace code to see *why* it failed.   The age old hardware
guy vs software guy debugging argument.  I would love to hear your
results on the Mimeo.  More data is good.  If it works, save me a
Mimeo and I'll order one ;-)

Dave...