mathog wrote: > 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: > > http://www.supermicro.com/products/chassis/2U/823/SC823S-550LP.cfm > > This is what that motherboard looks like without heat sinks: > > http://www.supermicro.com/a_images/products/Aplus/MB/H8DC8_spec.jpg > > 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). > > http://i19.photobucket.com/albums/b165/TeamScream/Wide-2.jpg > > Notice the 50% overlap in the heat sinks in the direction of the > airflow? > That is the overlap with more conventional heat sinks too. Yes, it > really > does feed hot air from CPU1 into CPU2. Putting a little wall in, > redirecting the hot air from CPU1 around CPU2 dropped CPU2's > temperature > by 4C. Nothing else I tried made a bit of difference - including > lowering > 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 > fans > 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 > CPU2. > 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. > For > this design airflow was taken into account. Note that the CPU sockets > are > spaced farther apart perpendicular to the air flow. It is very similar > hardware otherwise: > > http://www.opteronics.com/images/16a_MBLarge.jpg > > there are some pictures of these with heat sinks in place which may be > found > 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 > taller, > stuffed into an old 2U case scavenged from an old machine. In that > machine > the two CPUs run at very close to the same temperature. The component > layout > 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 > fan. > 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), > plus > removing the front panel and as much of the back panel as possible, > including > 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 > "Scotch-Weld"). > 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 > > http://parts.digikey.com/1/parts/440266-hot-melt-adhesive-vo-5-8-x2-3748-vo-tc.html > > is not as heat resistant as the 3731. Probably have to use 3748 > though, since at least > it can be purchased easily. > > Regards, > > David Mathog > mat...@caltech.edu > Manager, Sequence Analysis Facility, Biology Division, Caltech > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf
Hi David 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 the two? Gus Correa _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
