A Tyan S2466 gotcha

David Mathog mathog at mendel.bio.caltech.edu
Wed Nov 5 11:59:29 EST 2003

Has anybody else seen this?

Last week I was going nuts trying to figure out why one of
our Tyan S2466 nodes was running slower than all the others.
It was physically the same as the other nodes (1Gb memory,
S2466 motheboard, single Athlon MP 2200+) yet CPU bound jobs
ran about 25% slower on only this node.  Finally it crossed
my mind that maybe the vendor had somehow or other stuck
the wrong chip in it, and sure enough, /proc/cpuinfo showed
that one node having an Athlon MP 1600+.  Except it wasn't
really.  Simply rebooting the node changed /proc/cpuinfo
back to Athlon MP 2200+.

Apparently under some circumstances this motherboard will
throttle back from 266Mhz to 200Mhz, at which point it
misreports the identity of the CPU.  Asus mobos
do something similar when they shut down funny (for instance
on a power failure)but they stay at the slower "safe"
setting until it is changed manually in the BIOS.  This
Tyan board bounces back up to the higher setting on the
next reboot.

Anyway, the take home lesson seems to be that one should
scan the /proc/cpuinfo on all nodes following a reboot to
verify that all came up at the rated speed.

Is there some way to configure these nodes so that
they cannot drop into the lower speed? 


David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
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