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SubjectRe: crashes with no log messages
I have seen a number of messages that go like this: 'Last night my 
2.0.33 machine, Pentium II, etc etc crashed with no log messages...
what's wrong?' But none of these posters ever mention if the machine
was on an uninterruptible power supply and running powerd or something
else that would make for an orderly shutdown. Really, you should
mention this, because as Alan Cox pointed out Linux has a fundamental
bug in that if the computer loses its connection to a working power
supply it will crash with no logs. More than that, if there's a
brownout, or an EMF pulse, this can happen too. If you DON'T have your
system on a UPS, and your system crashes this way there's really no
point in posting.

Perhaps it's my experience with making and troubleshooting electronics
hardware that makes me amused at people's faith in the mechanical system
itself. It's amazing what a little extra heat, dust, etc on a
motherboard or add-in card will do, esp. if that card was designed
without much 'overhead' for external stress. Electronics can suffer
from cosmic rays of all things - flip a bit in a DRAM just like that.
For even more fun, you can get a bus loaded with peripherals in a state
with a certain combination of bit patterns that turn a bit into
something that's not a 0 and not a 1 - the chances might be 1 in a
quintillion or something but when you're talking a 300 Mhz machine,
well you can calculate about how often it'll happen and it's really not
that unlikely. Really, you should be amazed when things DON'T crash
with no error logs ....

About the only kind of hardware that I see that
doesn't crash like that more than, say, once in 5 years, is a machine
specifically designed by a capable system designer to be a server with
great ventilation, lots of fans, well made SCSI cables, redundant power
supplies, on a good UPS with monitoring, running Netware, OS/2, UNIX or
AS/400's system. If you have a low-cost desktop machine and get these
kinds of numbers, you're just lucky. Don't blame Linux, for goodness's
sake. If you see a crash with no logs running Linux on equipment rated
for life support systems, by all means, do post.

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