RE: Grief with Dejagnu; Testing gcc 2.95.3.test4 on SCO OS5.0.4

[David Korn <dkorn at pixelpower dot com>]

>See
>
>http://www.bitwizard.nl/sig11/
>
>for advice on how to determine whether this symptom is a software or a
>hardware problem, and, if it is hardware, what might be causing it.

  Someone (you, perhaps?) mentioned that site when this subject last came
up a few months ago.  I don't reckon it's disk trouble because I've tried
it with both file caching and virtual memory disabled.  I would believe it
could be some amazingly obscure marginal timing error in the RAM, but the
thing that gives me a hard time accepting that theory is that it has the
implication that 9 out of 10 DIMMs on the market are faulty in this way. 
I've experienced this problem both my couple-of-years-old name-brand PC
at work and my recent home build machine.  Different DIMMs from different
manufacturers years apart.  I've swapped DIMMs round left right and
center in that machine, because I did have a faulty (or just incompatible)
one at one point, but it showed up straight away (POST detected it, and
so did the memory checker).  I guess I'm still left with the possibility
of cache trouble.

>Some memory checkers are much better than others.  The one in the PC BIOS
>is near-worthless except for detecting that one of your DRAM chips is
>completely non-functional.

  Yes, I knew that, it's pretty obvious that something that checks 384M in
a second or two can't be very comprehensive!  Again, last time this
subject came up here, somebody recommended a very comprehensive memory
tester that I can't remember the name of, but it's really thorough (runs
off a DOS boot disk and has loads of different test patterns).  Running
that for days on end never showed any kind of errors at all.

  The problem is that nobody is really sure what the problem is, and 
whether there's just one problem or a variety of similar ones, and it's
very difficult to reproduce because even when it happens reliably (ie.
you can type 'make' over and over and it bombs at the same point each
time) it tends to go away the moment you try and get the debugger on it.
I would really like to know what's going on and if anyone would like
to lend me a gigaherz range 100-channel logic analyzer for a few months
I'll try and capture the event happening!

        DaveK
-- 
"Never give succor to the mentally ill; it is a bottomless pit."  
  -- William S. Burroughs


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