Path: utzoo!attcan!uunet!mailrus!iuvax!bobmon
From: bobmon@iuvax.cs.indiana.edu (RAMontante)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Memory Problem: How Best to Diagnose?
Message-ID: <49085@iuvax.cs.indiana.edu>
Date: 28 Jun 90 14:02:10 GMT
Organization: malkaryotic
Lines: 35

mjw06513@uxa.cso.uiuc.edu (Mary Winters) <1990Jun28.032323.5496@ux1.cso.uiuc.edu> :
	[ Memory upgrade; software upgrade; then... ]
| code provided, when all of a sudden a memory parity error burst onto the 
| screen. I rebooted, tried it again. Same thing. Checking the manuals, I found
| out that the IDE makes use of available extended and/or exapnded RAM. It
| appears that when the compiler swaps out to expanded RAM, a parity error is
| generated. I re-ran the memory tests, but the memory passed. I tried various 
| other things, but what finally worked was putting back my old memory SIMMs. 
|	[ description omitted ]
| What's the best memory testing software for a '386? Why would SIMMs which pass
| a "normal" test cause parity errors when TC++ tries to access extended RAM?


For what it's worth...

I added a bank of (used) 256K chips to my EMS board awhile ago, and let TC
put its editor up there.  Shortly afterwards I started getting corrupted
files during editing and compilation.  What I eventually discovered was that
the chips were flaky, but only failed slowly and after they'd been running
for long enough to warm up --- the EMS board's memory diagnostics passed
the chips, but when the TC editor put a file into that memory bank, some
bytes would flip bits *after twenty seconds or so*.

I finally diagnosed this by creating a file containing just the `-'
character over and over to fill the editor buffer.  In the time it would
take to page from one end of the file to the other, a few characters
would change to something else, which was easily detected visually.
(Tediously manual process, but easy.)  In my case, I wasn't getting any
parity error, possibly because I had turned off parity checking (or maybe
a bug in the EMS board).  In total, though, SIX of the nine chips had at
least one bad bit somewhere!

Ten bucks' worth of some more used chips seems to have solved my problem;
or maybe putting the EMS board in a different slot lets it run cooler.
But I'm a happy camper again.