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Old 2008-08-24, 07:16   #1
dans
 
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Oct 2002

3·7 Posts
Default Running the numbers

I’ve inadvertently setup a prime monster.

After being idle for over a year due to traveling overseas I’ve just started building a few prime-crunching machines. After browsing the local “used computer” gear ads I located someone selling off a bunch of Dell Precision 530 workstations (Dual Xeon 2.4GHz “dual core w/hyperthreading” and 512mb of RAM) and was able to nab them for a song.

Now, the question is… I’ve started setting these machines in my shop and they are burning power in copious amounts! I’ve noticed that I seem to be able to find modern Intel Q6600’s from the local used market for around $150/ea, throw in a $60 motherboard from Fry’s and some memory+case+power supply that I have spares of and I’m beginning to second guess the wisdom of buying the Dells.

How do I work this out? I’m hitting the 10M prime numbers, nothing else.

The Dells benchmark as follows (using 25.6v6 with the default settings) I’m assuming that the benchmark is only measuring one of the CPUs at a time (there are two per machine):
Intel(R) XEON(TM) CPU 2.40GHz
CPU speed: 2392.55 MHz, 2 hyperthreaded cores
CPU features: RDTSC, CMOV, Prefetch, MMX, SSE, SSE2
L1 cache size: 8 KB
L2 cache size: 512 KB
L1 cache line size: 64 bytes
L2 cache line size: 128 bytes
TLBS: 64
Prime95 32-bit version 25.6, RdtscTiming=1
Best time for 768K FFT length: 29.252 ms.
Best time for 896K FFT length: 34.850 ms.
Best time for 1024K FFT length: 38.668 ms.
Best time for 1280K FFT length: 50.089 ms.
Best time for 1536K FFT length: 62.085 ms.
Best time for 1792K FFT length: 73.542 ms.
Best time for 2048K FFT length: 82.431 ms.
Best time for 2560K FFT length: 107.126 ms.
Best time for 3072K FFT length: 135.259 ms.
Best time for 3584K FFT length: 161.081 ms.
Best time for 4096K FFT length: 181.111 ms.
Best time for 5120K FFT length: 230.585 ms.
Best time for 6144K FFT length: 289.379 ms.
Best time for 7168K FFT length: 352.118 ms.
Best time for 8192K FFT length: 408.414 ms.
Timing FFTs using 2 threads on 1 physical CPUs.
Best time for 768K FFT length: 28.455 ms.
Best time for 896K FFT length: 33.962 ms.
Best time for 1024K FFT length: 37.832 ms.
Best time for 1280K FFT length: 50.343 ms.
Best time for 1536K FFT length: 63.172 ms.
Best time for 1792K FFT length: 76.859 ms.
Best time for 2048K FFT length: 84.640 ms.
Best time for 2560K FFT length: 111.853 ms.
Best time for 3072K FFT length: 137.458 ms.
Best time for 3584K FFT length: 165.427 ms.
Best time for 4096K FFT length: 188.749 ms.
Best time for 5120K FFT length: 247.139 ms.
Best time for 6144K FFT length: 315.882 ms.
Best time for 7168K FFT length: 398.197 ms.
Best time for 8192K FFT length: 475.112 ms.
Timing FFTs using 4 threads on 2 physical CPUs.
Best time for 768K FFT length: 17.949 ms.
Best time for 896K FFT length: 21.039 ms.
Best time for 1024K FFT length: 24.226 ms.
Best time for 1280K FFT length: 33.036 ms.
Best time for 1536K FFT length: 38.681 ms.
Best time for 1792K FFT length: 46.397 ms.
Best time for 2048K FFT length: 58.860 ms.
Best time for 2560K FFT length: 75.734 ms.
Best time for 3072K FFT length: 92.014 ms.
Best time for 3584K FFT length: 107.983 ms.
Best time for 4096K FFT length: 122.882 ms.
Best time for 5120K FFT length: 166.622 ms.
Best time for 6144K FFT length: 218.478 ms.
Best time for 7168K FFT length: 293.017 ms.
Best time for 8192K FFT length: 346.373 ms.
Best time for 58 bit trial factors: 13.345 ms.
Best time for 59 bit trial factors: 13.167 ms.
Best time for 60 bit trial factors: 13.104 ms.
Best time for 61 bit trial factors: 13.182 ms.
Best time for 62 bit trial factors: 13.257 ms.
Best time for 63 bit trial factors: 13.289 ms.
Best time for 64 bit trial factors: 16.261 ms.
Best time for 65 bit trial factors: 16.093 ms.
Best time for 66 bit trial factors: 16.174 ms.
Best time for 67 bit trial factors: 16.069 ms.

My “primary” machine happens to be a Q6600 with lots of memory (4Gb vs. 512mb):
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
CPU speed: 2400.02 MHz, 4 cores
CPU features: RDTSC, CMOV, Prefetch, MMX, SSE, SSE2
L1 cache size: 32 KB
L2 cache size: 4096 KB
L1 cache line size: 64 bytes
L2 cache line size: 64 bytes
TLBS: 256
Prime95 32-bit version 25.6, RdtscTiming=1
Best time for 768K FFT length: 18.509 ms.
Best time for 896K FFT length: 22.380 ms.
Best time for 1024K FFT length: 26.265 ms.
Best time for 1280K FFT length: 32.764 ms.
Best time for 1536K FFT length: 40.435 ms.
Best time for 1792K FFT length: 48.591 ms.
Best time for 2048K FFT length: 53.459 ms.
Best time for 2560K FFT length: 71.887 ms.
Best time for 3072K FFT length: 86.916 ms.
Best time for 3584K FFT length: 102.946 ms.
Best time for 4096K FFT length: 117.644 ms.
Best time for 5120K FFT length: 147.680 ms.
Best time for 6144K FFT length: 184.824 ms.
Best time for 7168K FFT length: 224.417 ms.
Best time for 8192K FFT length: 245.190 ms.
Timing FFTs using 2 threads.
Best time for 768K FFT length: 10.449 ms.
Best time for 896K FFT length: 13.022 ms.
Best time for 1024K FFT length: 15.941 ms.
Best time for 1280K FFT length: 20.130 ms.
Best time for 1536K FFT length: 24.743 ms.
Best time for 1792K FFT length: 31.635 ms.
Best time for 2048K FFT length: 34.748 ms.
Best time for 2560K FFT length: 45.853 ms.
Best time for 3072K FFT length: 54.676 ms.
Best time for 3584K FFT length: 64.933 ms.
Best time for 4096K FFT length: 75.801 ms.
Best time for 5120K FFT length: 96.459 ms.
Best time for 6144K FFT length: 114.121 ms.
Best time for 7168K FFT length: 141.458 ms.
Best time for 8192K FFT length: 164.056 ms.
Timing FFTs using 3 threads.
Best time for 768K FFT length: 18.557 ms.
Best time for 896K FFT length: 21.764 ms.
Best time for 1024K FFT length: 32.474 ms.
Best time for 1280K FFT length: 25.134 ms.
Best time for 1536K FFT length: 31.151 ms.
Best time for 1792K FFT length: 38.685 ms.
Best time for 2048K FFT length: 44.255 ms.
Best time for 2560K FFT length: 53.242 ms.
Best time for 3072K FFT length: 68.883 ms.
Best time for 3584K FFT length: 80.478 ms.
Best time for 4096K FFT length: 92.329 ms.
Best time for 5120K FFT length: 112.051 ms.
Best time for 6144K FFT length: 144.339 ms.
Best time for 7168K FFT length: 171.051 ms.
Best time for 8192K FFT length: 188.729 ms.
Timing FFTs using 4 threads.
Best time for 768K FFT length: 17.669 ms.
Best time for 896K FFT length: 19.523 ms.
Best time for 1024K FFT length: 28.690 ms.
Best time for 1280K FFT length: 24.258 ms.
Best time for 1536K FFT length: 29.561 ms.
Best time for 1792K FFT length: 35.118 ms.
Best time for 2048K FFT length: 39.919 ms.
Best time for 2560K FFT length: 53.968 ms.
Best time for 3072K FFT length: 63.198 ms.
Best time for 3584K FFT length: 75.066 ms.
Best time for 4096K FFT length: 84.503 ms.
Best time for 5120K FFT length: 108.031 ms.
Best time for 6144K FFT length: 131.074 ms.
Best time for 7168K FFT length: 156.161 ms.
Best time for 8192K FFT length: 186.306 ms.
Best time for 58 bit trial factors: 4.436 ms.
Best time for 59 bit trial factors: 4.512 ms.
Best time for 60 bit trial factors: 4.417 ms.
Best time for 61 bit trial factors: 4.433 ms.
Best time for 62 bit trial factors: 7.446 ms.
Best time for 63 bit trial factors: 7.478 ms.
Best time for 64 bit trial factors: 6.902 ms.
Best time for 65 bit trial factors: 6.855 ms.
Best time for 66 bit trial factors: 6.897 ms.
Best time for 67 bit trial factors: 6.851 ms.

So, if you’ve read this far, I am trying to compare the efficiencies of running a Quad-Core 2.4GHz Intel Q6600 vs. a Dell Precision machine with Dual-Xeon 2.4GHz processors.

If I am reading the benchmarks above properly, the Q6600 is simply stomping on the Dual-Xeon Dells (as expected) but is it worth replacing the cheap Dells with more Q6600 setups? If so, what is the ratio (read: one Q6600 replaces two of the Dual-Xeon Dells…?) I haven’t even run out the power consumption numbers at this point.

FWIW, I have 10 of the Dells, I can probably sell them for $100-150 each, so I could replace the 10 Dual-Xeon 2.4GHz machines with around 5 or 6 new quad-core Q6600s.

Many thanks,
-Dan “Gee, my shop is getting warm!"
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Old 2008-08-24, 07:52   #2
Batalov
 
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"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

22·3·5·157 Posts
Default

Dude, you hit the nail on the head. I have one of those Dells (well it's a bit pimped up; it has 2 4-core Xeons E5345) at work and under Prime95 on 7 cores (which only amount to ~5x 1-core productivity; the 8th - actually makes it slower still in thoughput) -- I cannot breathe in my office. The goddamn thing is a furnace. (why not kill the Prime95? - read the "You may be addicted to GIMPS, if..." )

At home my Q6600 (with 4 cores, obviously) definitely beats the Dell 8-core sucker hands down and is nowhere near warm.

But as for your main question - it's tricky. Play with all the $ numbers; don't forget the electric bill and simply the comfort of coolness.

Good luck,
-Serge
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