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Subject(OT) md5sum proving to be an EXCELLENT memory test
Because the subject of "bad RAM" comes up from time to time on this list, I 
thought I would post an observation I made over the weekend. I was working
with some server boxes with "generic" RAM that would mis-behave from time
to time, and I really didn't understand why that would happen. The
misbehavior included some OOPSes from time to time, but they would be
random and so I didn't report them.

Then I started to grab Red Hat Linux version 9, and because the server
boxes were the only ones with enough open disk space I started to download
the ISO images to them. Imagine my surprise when I went to run md5sum to
check the download -- they would fail the test. Perform the test multiple
times, and the failure pattern would CHANGE. (Copy the ISOs to another
system via sftp, along with the MD5SUM, and they checked as
perfect.) Perform md5sum on the files on the server and save the results,
and the signatures would be different from run to run on the same files.

Incompatible RAM.

Proof: do a kernel computer, get signal 11. Put the "right" RAM in the
boxes (in this case, a Viking PE8641U4SN3L-CL3 64-MB stick in an Intel
CA810E motherboard) and both md5sum and a kernel compile worked just swell.

By the way, md5sum on small files worked perfectly on these server boxes
with IFA (Taiwan) 128-MB RAM installed, but on large files it would create
the varied signatures.

So, along with the test of compiling a kernel and seeing if you get signal
11 messages, you can also load up some large files and run md5sum on them a
couple of times. With six ISO images totalling 1.4 GB, it took a 500-MHz
Pentium II about five minutes to run through the files and show the errors
-- an order of magnitude faster than trying to do a kernel compile.


Stephen Satchell

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