Tuesday, March 17, 2009

a welcome to two baby brothers

well, I am definitely not given to moderation. Actually, now that I've spent all the money I am :-)

two new machines:

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very similar to cudak1 described below, you wouldn't tell them apart from outside, so I'm not posting pictures today.
the same overall profile of a quiet, small, personal supercomputer. an office machine on which to learn cuda and develop applications, running 64-bit linux fedora 10 and cuda, as well as doing everything else you expect of a desktop workstation. (I crammed like 100 audio cd's into my rhythmbox files.)

major differences: X58 architecture with 4-core (8-thread) Nehalem Intel chip (2.68 GHz, I believe). only slightly overclocked gpus: 720 cores on 3 nVidia GeForce GTX280 H2O (as opposed to H2OC in original cudak1). Different communication bandwidths via PCI-e bus on a P6T6 workstation beard by Asus. has a multiplexer preventing a permanent degradation of a link to the middle graphics card, like in the 790i architecture. That doesn't mean you can get 3 x (5-6)GB/s flow concurrently to all 3 cards, but maybe that's an unlikely request in practice. cpu simply cannot handle 3 cards at max speed. at least all three cards are now on a more level playing field. they reach the same peak bandwidth of 5.8 GB/s, which Asus calls "true 3-way SLI". whatever. these motherboards are rare though, I understand.

the new Intel cpu also includes its memory controllers, offloading tasks form the previously overworked or at least overheating northbridge. and that means: finally no noisy, microscopic northbridge fan on the P6T6 mobo.

a nice surprise: you open up a system monitor and there are 8 separate cpus reported and graphed (twice the number of actual cores on Nehalem thanks to hyperthreading).

at some point I may describe one technical mod which I made to thermally stabilize the motherboard. I revesed all the Zalman's fans and am now blowing the hot air from the radiator outside, as God intended it. higher coolant and card temps (still comfortably low vis-a-vis specs) but, importantly, lower component and air temps inside the box --> no thermal hang-ups of the motherboard.

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this one is a step-brother, not a twin brother of cudak1 vel Z-machine. Its an air-cooled monster
in a Thermaltake Armour full-tower case, with watercooling applied to the Nehalem cpu, but with 3 aircooled GTX295 dual-gpu cards. So 6 gpus this time not 3, although each a little slower (main clock ~579 MHz, as opposed to the overclocked H2OC @ 680 MHz). That translates to a theoretical peak performance of 5+ TFLOPs. Benchmarks heat gpus up to 91 C, and the system becomes a bit noisy.
oh well... the noise is a fair price to pay for a theoretical performance of a small campus-scale computing center. (I made a small mechanical modification to improve air flow, preemptively. So far I could not crash this system thermally, but I haven't tried extra hard, "just" 6 or 8 benchmarks running at the same time..)

total system cost of cudak2 and 3 was on the order of $5.5k CAD each; that is currently something like $4.4k USD. more info later.

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