More Bringing up a CPM - test-drb@ccmp.vtda.org

2 Jun 1999

please see embedded remarks below.

Dick

-----Original Message-----
From: Allison J Parent &lt;allisonp(a)world.std.com&gt;
To: Discussion re-collecting of classic computers
&lt;classiccmp(a)u.washington.edu&gt;
Date: Tuesday, June 01, 1999 9:00 PM
Subject: Re: Re[4]: More Bringing up a CPM

...
 <Even if you don't intend to use PROMs in your
final device, I'd certainly
<recommend you build a few PROMS which make the processor do rudimentary
<things and perhaps which make the DMAC do the same things.  You then have
<simple tools with which to troubleshoot your memory interfaces.

that can be helpful.  I just use the CPU executing junk FF/00 or whatever
else the bus lets it see, 

This might work but is rarely predictable.

...
 <After reading about the problems you're having,
I think I'll fetch the 124
<LA out onto the patio as well.

I troubleshoot 90% of my s100 problems with a good logic probe and
a DVM.  The rare case I've dragged out the scope it was handy but usually
because I missed something stupid.  The recent NS* bring up required the
logic probe, its where I spotted a missing Mwrite/ (jumper smeared off the
cpu board). 

The logic analyzer is handy for gathering information about what a given
board does in a specific environment.  I though I'd like to have pictures of
the cycle at the bus to correlate with the same cycle at the DRAMs, since I
have over a dozen DRAM boards to check out.  This will give me information
about the various DRAM boards as well as the cycle timing generated by the
various CPU's.

...
 With rare exception and all if a board doesn't work
scoping it may or may
not help.  just follow the logic with a logic probe as likely it's a chip
or socket failure.  The reason is the board worked, was sold working and
if it were good it should still work.  The exception is when you have bus
incompatability problems and a scope will not help unless your going to
alter the board to make it work assuming it was not also broken.

I've found the 'scope and LA more trouble to use than a meter and a logic
probe, but I've also learned that I get more useful information about DRAM
boards by looking at their DRAM control strobes and timing relative to the
memory access strobes and data than I could get with a meter and logic probe
under any circumstances.  So many DRAM cards are at least partly timed with
one-shots, a tool which merely tells you sommething's happening but doesn't
tell you what, is not of much use in THIS case.
...

Allison