[Beowulf] materials for air shroud?
gus at ldeo.columbia.edu
Fri Sep 16 10:54:32 EDT 2011
> A not so short story about air flow...
> Yesterday I did some experimenting with different baffles and ducts,
> each built temporarily
> out of the cardboard backs from yellow notepads and held together with
> masking tape. (Not worried
> about a fire, since it only ran for 10 minutes at a time like that, and
> I was right there to
> yank the plug and rip out the cardboard if something went wrong.) The
> system has a Supermicro H8DC8
> motherboard in a Supermicro case. This one:
> This is what that motherboard looks like without heat sinks:
> and here is a very similar motherboard with heat sinks in place (but
> not my
> motherboard, which uses conventional flat passive heat sinks, not the
> big curved
> orange monsters in the picture).
> Notice the 50% overlap in the heat sinks in the direction of the
> That is the overlap with more conventional heat sinks too. Yes, it
> does feed hot air from CPU1 into CPU2. Putting a little wall in,
> redirecting the hot air from CPU1 around CPU2 dropped CPU2's
> by 4C. Nothing else I tried made a bit of difference - including
> the "ceiling" over CPU2. CPU2 is still hotter than CPU1 even with that
> fix. The reason it will not get any better is that while there are 4
> in the system, they are not placed very well for this motherboard. The
> first one sends all of its air into the PS and so doesn't cool the CPUs
> at all. Totally a waste since the PS has a fan already. The next fan
> is partially blocked by CPU1, so maybe 3/4 of its air is available for
> CPU1 then gets the remaining 1/4 of that fan, and most of the next fan,
> so around 1 whole fan's worth. The last fan blows over the chipset and
> PCI slots, again, with no contribution to cooling the CPUS.
> For comparison, here is a Rio-works HDAMA motherboard which we have.
> this design airflow was taken into account. Note that the CPU sockets
> spaced farther apart perpendicular to the air flow. It is very similar
> hardware otherwise:
> there are some pictures of these with heat sinks in place which may be
> by google image search for "HDAMA motherboard" - I didn't want to link
> to them as they
> all seem to be on ebay and those links could disappear at any time.
> Note how the
> heatsinks do not overlap in the direction of the air flow? We have one
> of these,
> with passive heatsinks of approximately the same shape, but a bit
> stuffed into an old 2U case scavenged from an old machine. In that
> the two CPUs run at very close to the same temperature. The component
> in the case is very similar to the Supermicro except that the heat
> sinks are not
> overlapping, so here there is a fan lined up directly on center with
> each CPU,
> plus one to cool the chipset/PCI slots. The PS gets by on its internal
> The old case has been "optimized" for air flow by the simple expedient
> of placing
> the 3 fans as just described (originally there was just one fan in it),
> removing the front panel and as much of the back panel as possible,
> the shield that normally goes around the jacks on the motherboard.
> The HDAMA machine is pretty darn ugly, but it definitely "breathes"
> better than
> the Supermicro.
> I found a product with the perfect properties for sticking
> polypropylene sheets
> together. This is 3M "Jet-melt" 3731 hot melt adhesive. (Also called
> Unfortunately I need about 2cc of it, but nobody sells it in sizes less
> than 11 pounds!
> The only place that sells anything in this whole 3M hot melt line as
> single sticks is Digikey,
> and the one they sell
> is not as heat resistant as the 3731. Probably have to use 3748
> though, since at least
> it can be purchased easily.
> David Mathog
> mathog at caltech.edu
> Manager, Sequence Analysis Facility, Biology Division, Caltech
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It may complicate matters too much, but to avoid blowing warm
air over CPU2 on the SuperMicro board, is it possible to make two ducts,
slightly S-shaped ( __/``` ), one blowing air on the (cpu-1-RAM)+CPU2,
the other on CPU1+(cpu-2-RAM)?
Or perhaps a single duct, but include an S-shaped wall/divider between
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