Re: Apple 1 CFFA1 AND FORTH +

[mwillegal <mike@willegal.net>]

On Nov 2, 12:53 pm, David Schmenk <dschm...@gmail.com> wrote:
> 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...

Actually checking that writing one location doesn't affect another
location
is exactly what the address in address tests do.  I believe I pulled
up an address pin on a ram chip  at one point during development
of this test tool to make sure the test would properly find the fault,
which it did.

Trying this software out is pretty high on the list of things to do.
I really
don't expect different results from the Obtronix, but maybe I'll be
able
to find root cause of the problem.

Regards,
Mike W.