On Fri, 9 Jan 2004 11:58:36 +0000, Terry Pratchett
<tpratchett@unseen.demon.co.uk> wrote:

No new software has been put on the machine, no specs have been altered, 
and in every other respect it appears to be working fast and 
efficiently.  Can anyone give me a clue about what might be happening?
-- 

There's probably another process poisoning your processor cache.  Have
a look at all processes running, the stuff in your systray, and
anything else like services to see if something is consuming
unexpected amount of resources.  Also, have you updated your AV
software to a new version?  It's possible that the AV is inspecting
the .sah files at each write.  That's a killer too.  You might want to
try excluding *.sah from your AV scanning.

An example:  I saw one instance of a TV tuner card that had a
background process running that interrogated the remote controller
sensor every so often -- on the order of hundreds of times a second,
probably.  When that process was running it cut the throughput of WUs
by more than 50%, even though the process itself consumed very little
resources, as measured by CPU time consumed.  What it did manage to do
is poison the cache hundreds of times a second, forcing a reload from
slow main memory.