[Beowulf] The fan from hell

Martin Siegert siegert at sfu.ca
Thu Jun 9 17:42:49 PDT 2005

Hi David,

On Thu, Jun 09, 2005 at 02:56:56PM -0700, David Mathog wrote:
> Today I distributed database fragments out from the main server
> to the 20 compute nodes.  This required the server to run gunzip
> pretty much continuously for a couple of hours. The net result of
> which was that CPU1's temperature rose from 55C to 60-61C.
> Normally the fan on CPU1 sits happily at 5033 RPM. However
> today it started to slow down.  In fact it slowed down below
> 3000RPM, which triggered an automatic shutdown of the server.
> After a bit of experimentation I've now determined that
> this wasn't a coincidence. This CPU fan really does run
> slower when the CPU gets hotter.  It takes a
> few minutes before it starts to slow down, but slow down it
> does.  Not exactly the desired response for a fan on a hot CPU!
> This is on an Athlon MP 2000+ processor and the fan is Dynatron
> model that AMD used with the boxed CPU.
> Any of the system vendors (or anybody else) out there have a
> preferred brand of 60mm fan that doesn't slow down at 60C?

We are using fans from Delta Electronics, model EFB0612HHA, which
come with the Alpha heatsinks on our Athlon MP2800+ (96 nodes).
They usually run between 5400 and 5600 RPM and processor temperatures
between 50 and 60C. I have seen cpu temperatures as high as 72C at
which point the box shutsdown. I have never seen the fan speed to
change with cpu temperature.

The heat sinks and fans that came with the boxed cpus were useless
for use - the nodes would shutdown all the time.

- Martin

Martin Siegert
Head, HPC at SFU
WestGrid Site Manager
Academic Computing Services                        phone: (604) 291-4691
Simon Fraser University                            fax:   (604) 291-4242
Burnaby, British Columbia                          email: siegert at sfu.ca
Canada  V5A 1S6

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