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SeaMicro Unveils 512 Atom-Based Server
1sockchuck writes "Stealthy startup SeaMicro has unveiled its new low-power server, which incorporates 512 Intel Atom CPUs, a load balancer and interconnection fabric into a 10u server. SeaMicro, which received a $9.3 million government grant from DOE to develop its technology, says its server uses less than 2 kilowatts of energy — suggesting that a single rack with four SeaMicro units and 2,048 CPUs could draw just 8 kilowatts of power. Check out the technical overview, plus additional coverage from Wired, GigaOm and VentureBeat."
That's not too hard to calculate. I usually budget 2 A for a dual-CPU 1u server. At 120 V, that's 240 W. 8 kW divided by 240 W = 33u of servers. Multiplied by 12 cores (allowing for the new X5600 series, ignoring hyperthreading on both Atom and Xeon), you get 396 total cores of standard Xeon in 8 kW. Meanwhile, they're advertising 2048 Atom cores in the same amount of power. So, the real question becomes how powerful ~5 Atom cores are compared to 1 Xeon core.
Almost, but not quite. The things that suck about the atom:
1. double precision. Use a double, and the Atom will grind to a halt.
2. division. Use rcp + mul instead.
3. sqrt. Same as division.
All of those produce unacceptable stalls, and annihilate your performance immediately. So don't use them!
Now, you'd imagine those are insurmountable, but you'd be wrong. If you use the Intel compiler, restrict yourself to float or int based SSE instuctions only, avoid the list of things that kill performance, and make extreme use of OpenMP, they really can start punching above their weight. Sure they'll never come close to an i7, but they aren't *that* bad if you tune your code carefully. Infact, the biggest problem I've found with my Atom330 system is not the CPU itself, but good old fashioned memory bandwidth. The memory bandwidth appears to be about half that of Core2 (which makes sense since it doesn't support dual channel memory), and for most people that will cripple the performance long before the CPU runs out of grunt.
The biggest problem with them right now is that they are so different architecturally from any other x86/x64 CPU that all apps need to be re-compiled with relevant compiler switches for them. Code optimised for a Core2 or i7 performs terribly on the atom.