mersenneforum.org POWER CONSUMPTION idle versus Prime95
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 2005-01-14, 08:26 #1 Peter Nelson     Oct 2004 232 Posts POWER CONSUMPTION idle versus Prime95 WARNING: HIGH VOLTAGE! I have been experimenting with a power analyser Model2000MU-UK made by www.prodigit.com This device is inserted between the mains electricity supply and the device under test, and displays: Voltage(V) Current in Amps(A) Active Power in Watts(W) Apparent Power in Volt-Amps(VA) AC Frequency(Hz) Power Factor(PF) Energy quantity of consumption(KWhour) Time elapsed this test. Voltage and current are RMS (root mean square) values. There have been guesses elsewhere on this forum as to how much extra electricity a business would consume by joining primenet versus sitting idle. My intent is not to discourage running Primenet but to make available some factual information on the basis of which to make such a decision. I'm also interested in how much it costs to run my computers 24x7, and which ones are more efficient than others. By removing components I can measure the effect this has on power consumption. After lots of experimentation and measurement I will post my findings here. When reading the results, KWh values are comparable anywhere, but remember that here in the UK our voltage is nominally 240volts at 50Hz. If you live in the USA or use a different voltage supply the Amps you experience will be different because the voltage is different. I would be interested in anyone else doing comparative measurements or comments on my results.
 2005-01-14, 09:08 #2 Peter Nelson     Oct 2004 232 Posts Tests on four computers I have tested: A)Toshiba Satellite Pro 4280 laptop (pentium III at 497MHz) B)Compaq Deskpro P733 (pentium III at 730MHz) C)Self-build Celeron D320 (2.4Ghz overclocked to 2.7 GHz) on Gigabyte 865G board 2x512MB DDR socket 478 D)Self-build Pentium 4 @ 3.0GHz NOT overclocked on Intel 865G board+ATI9600XT graphics 2x512MB DDR socket 478 Calculations assume 24x7 operations. Simply scale down if you only power up during the day etc. Voltage was in the range 238V - 243V but relatively stable. All readings vary a little, and are subject to rounding and reading errors. Decimal places are arbitrary, at my discretion. Costs are calculated based on 5 pence per unit (KWhour) which is roughly the charge for residential customers in the UK. Substitute your own cost per KWH in your own currency as appropriate. Each configuration was run for up to 8 hours in some cases and consumption scaled up to a day and year for comparison. It's very cool how the watts, amps etc jump up when mprime or prime95 is invoked. PENTIUM III@500MHz System A:0.5333KWH/day=194.8KWH/year without Prime @ 5p=£9.74pa System A:0.6353KWH/day=232.04KWH/year RUNNING Prime @ 5p=£11.60pa EXTRA 37.24 KWH/year = EXTRA £1.86/year For info A idle: 0.18A 21W 43VA For info A running: 0.3A 38W 75VA PENTIUM III@733MHz System B:0.8426KWH/day=307.74KWH/year without Prime @5p=£15.39pa System B: 1.1623KWH/day=424.54KWH/year RUNNING Prime @5p=£21.23pa EXTRA 116.8 KWH/year = EXTRA £5.84/year For info B idle:0.27A 35W 66VA For info B running: 0.36A 50W 86VA CELERON D@2.7Ghz System C:2.09KWH/day=763.49KWH/year without Prime @ 5p=£38.18 System C:3.69KWH/day=1347.77KWH/year RUNNING Prime @5p=£67.39 EXTRA 584.82KWH/year=EXTRA £29.21/year For info C idle 0.61A 91W 148VA For info C running 1.07A 155W 258VA PENTIUM4(NORTHWOOD)@3.0GHz System D:2.4KWH/day=876KWH/year without Prime @5p=£43.83 System D:4.1143KWH/day=1502.74KWH/year running Prime @5p=£75.14 EXTRA 626.74KWH/year=£31.31/year For info D idle 0.5A 96W 120VA For info D running 0.85A 168W 207VA CONCLUSION For typical systems in use today, running software for primenet does incur additional cost due to the rise in electricity consumed. Such increases can be quantified. It is worthwhile to compare the energy consumption of different hardware configurations. I have seen TCO (total cost of ownership) calculated over 3 years. When making heavy use of the cpu (as in Prime95/Mprime) the cumulative cost of electricity may approach the purchase cost of the components or system.
 2005-01-14, 09:24 #3 Peter Nelson     Oct 2004 232 Posts Power consumption and overclocking I experimented with the Celeron D 320 system (designed for 2.4GHz) I usually run it at 2.7GHz (overclocked moderately but it can also be overclocked to 3GHz or more. For info, System C(CeleronD) runs with cpu temp around 34 degrees C. System D(Northwood P4) runs with cpu temp around 44 degrees C. Both are using Intel's air cooling. In the test above it is recorded: idle: 0.61A 91W 148VA running: 1.07A 155W 258VA My next step was to remove some surplus hardware Extra cooling fan (leaving the one on the cpu and case) Four way fan controller SATA to IDE adapter board This dropped the power to: idle: 0.59A 83W 136VA running: 1.00A 147W 243VA The above was at 2.7GHz. I also tried the unclocked 2.4 speed: idle: 0.56A 83W 136VA running: 0.92A 138W 227VA And overclock to 3GHz speed: idle: 0.6A 87W 144VA running: 1.07A 158W 261VA So, as you overclock the system it uses more power.
 2005-01-14, 09:31 #4 Peter Nelson     Oct 2004 52910 Posts Saving power by removing hard and optical drives My next optimisation was to remove my hard drive and DVD drive from the Celeron system. I was able to boot linux using a floppy disk which also contained the prime software. Now, the idle system consumes: 0.51A 73W 124VA And when running mprime: 0.91A 136W 222VA This was at my standard overclock of 2.7GHz It's also worth noting that if you didn't just leave the system idle but put it in or let it timeout and powerdown into standby mode, it only uses 0.06A 6W 15VA Removing the power plug would reduce this to zero but neither of these will get any exponents tested.
 2005-01-14, 09:32 #5 Dresdenboy     Apr 2003 Berlin, Germany 192 Posts Results are as expected. Another interesting calculation would be the cost per iteration using a 1280K FFT or so.
 2005-01-14, 09:37 #6 Peter Nelson     Oct 2004 232 Posts Taking out the VGA and hyperthreading power consumption I took the same approach with my P4 I removed the 9600XT graphics card and used the onboard Intel extreme graphics 2 in the chipset instead. On the P4 system I tried measuring consumption with and without Hyperthreading enabled. There was no difference to power in the idle system and minimal increase when running mprime. This gave: 0.46A 87W 111VA when idle 0.81A 159W 194VA running prime, no hyperthreading 0.82A 163W 201VA running prime, hyperthreading enabled. I turned hyperthreading back off again the way the system normally is.
 2005-01-14, 09:43 #7 Peter Nelson     Oct 2004 232 Posts Removing drives again to reduce power consumption The P4 system contained two SATA hard drives and a PCI card to support them. There was also a DVD optical drive. Taking the same approach as with the Celeron D system I removed these components and once again tried running Mprime from a linux boot floppy. Now the results were: P4 driveless idle: 0.34A 60W 82VA P4 driveless running: 0.68A 132W 162VA Conclusion: a system using network or floppy booting will be more energy efficient for running so is desirable if these components are not required for other uses of the machine. In comparing the CeleronD and P4 systems, please note the PSUs were both rated at "550W" but differed in manufacturer and quality. The CeleronD used a QTEC PSU while the P4 used a more expensive (and maybe more efficient) PSU branded EZ-COOL.
 2005-01-14, 09:50 #8 Peter Nelson     Oct 2004 232 Posts Speed comparison for the above systems I have given details and power consumption for my P4 and Celeron D systems above. I here provide iteration speed benchmarks. From these you could work out electricity cost per iteration or electricity cost per exponent. Time for iteration in ms (FFT size, my P4 left, my CeleronD right) 384K 11.893, 16.227 448K 14.217, 19.759 512K 16.250, 21.899 640K 19.439, 26.783 768K 23.719, 32.290 896K 28.028, 39.116 1024K 31.303, 42.686 1280K 40.896, 56.825 1536K 50.533, 69.411 1792K 59.986, 87.102 2048K 67.633. 97.131 The Celeron D isn't as fast but it's a cheaper system to build and uses less power.
 2005-01-14, 10:27 #9 Peter Nelson     Oct 2004 232 Posts Cost of testing an exponent Dresdenboy, Thanks for your question about cost per iteration, (which will be miniscule), I think you're really interested in how much electricity bill money to test an exponent. OK, you will see I have now posted the time per iteration for various FFT sizes on the machines I tested so you can do exactly that calculation. You were interested in 1280K FFT size, which on SSE2, is used for exponents in the range 20.05 million through 24.93 million. A day's processing on the Celeron D costs 3.69KWH*5p=18.45pence (feel free to convert to Euros if you want) In this day, it can test 1520457 iterations at 56.825msec each. In the same day, my P4 costs 4.1143KWH*5p=20.57pence to run And it will test 2112676 iterations at 40.896msec each. Bigger exponents require more iterations you can either multiply up the time per iteration to get time elapsed for a LL test OR you could note how long a test takes (couple of months?) and multiply by the cost of electricity per day. Two months CeleronD costs £67.39/year divided by 6 = £11.23 Two months Pentium4 (note would do 38% more work in this time) but costs £75.14/6=£12.52 Also note the P4 system cost quite a bit more than the Celeron, maybe £100 extra for the processor? circa £150 vs £50 for the Intel chip excluding other components. This comparison is for my bare figures before I started stripping out drives and graphics cards.
 2005-01-14, 11:18 #10 Dresdenboy     Apr 2003 Berlin, Germany 192 Posts So the P4 costs 9.74p per 1M iterations, while the C-D costs 12.13p for the same amount of work. But still - as you've already pointed out - the higher cost for the P4 would surely outweigh these savings.
 2005-01-16, 19:42 #11 patrik     "Patrik Johansson" Aug 2002 Uppsala, Sweden 1A916 Posts I earlier posted some measurements here but since formatting changed when the forums were moved (or upgraded?), I repost it here. I didn't have time to make any further measurements of my newer computers. All below are P4 Northwoods: Code:  DELL Dimension 4550 Tyan Trinity 510 ASUS P4S333 2399 MHz 1907 MHz 2571 MHz Off 10 W 8 W 11 W Idle 87 W 76 W 76 W ECM Stage 1 135 W 110 W - P-1 Stage 1 145 W 118 W 135 W P-1 Stage 2 142 W - 131 W LL test 144 W 118 W 135 W

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