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Discussion on Article:
PC Power Consumption: How Many Watts Do We Need?

Started by: sstass | Date 06/07/09 10:55:26 PM
Comments: 24 | Last Comment:  07/07/09 11:59:14 AM

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Should've overclocked CPU and GPU. Together and separately. Would be insteresting to see total system power consumption with i7 920 o/c to ~4Ghz
I bet CPU o/c would add another 40W or so, plus video card o/c, another 30-40W. And we're at 600 easy. Add another 2-3 HDDs (who has 1 HDD nowadays anyway), and that's 30W+ more. And what about after market cooling and extra fans? Or maybe water cooling? We could get to 700W under load. Granted, 800W PSU would do just fine. However, a 1KW PSU would be running under 40-50% load most of the time - sweet spot for power efficiency.
0 0 [Posted by: sstass  | Date: 06/07/09 10:55:26 PM]
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The sweet spot for PSU power efficiency is 50-75%. See reviews covering the launch of the 80PLUS standard.
0 0 [Posted by: counter anecdote  | Date: 06/08/09 02:17:12 AM]
I agree that some overclocking should have been tested. I bet the majority of people who are regulars here who will read this have overclocked at least once in their life .

Also, there should have been an "Extreme" gaming rig, with 4-way SLI, Intel i7 975 OCed, watercooling, you know, the whole 9 yards! A system like that would be hitting at least 800-1000 if every component was stressed to the max. If you look at the efficiency range of the PSU heavyweights, it's around 800w or so, so of course people are going to be buying 1000-1200w PSU.

I will agree though, that 1500w power supplies are kind of overkill. I'd never buy one :p.
0 0 [Posted by: ezekiel 08  | Date: 06/08/09 06:03:19 AM]
Overclocking tests are on the way... patience!
0 0 [Posted by: Oleg Artamonov  | Date: 06/08/09 10:51:57 AM]
Awesome! Can't wait to read it!

*goes to check if article has been updated yet*

0 0 [Posted by: ezekiel 08  | Date: 06/11/09 05:55:58 AM]

Congratulations, you did a beautiful job Mr. Artamonov.

I have never seen such a detailed and forthright look at the true challenge of measuring consumed power in a PC. Your decision to build a dedicated 8 channel current metering card is brave and brilliant. Being an electronics technician who sometimes works in the solar industry, I can deeply appreciate the difficulty in measuring multi-channel DC current systems.

But of course, it begs the question: When can we buy your current measurement card and software?

And perhaps a follow up question: What software / hardware development tools, and what PCB fab services did you choose for this project?

Of course, I fully understand if you don't want to make announcements just yet, but here's to hope. You have done an eloquent job of a gnarly problem that 99% of everyone else seem to simply sidestep.

0 0 [Posted by: Crisspy  | Date: 06/08/09 10:22:03 AM]
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Sorry, but it's not for sale now. May be later, but I can't tell any specific date.
And perhaps a follow up question: What software / hardware development tools, and what PCB fab services did you choose for this project?
Nothing extraordinary. Eagle ( to draw schematic and PCB, Arduino IDE ( to program MCU and Embarcadero C++ Builder to wrote PC software. PCB fab is, cheap and very fast, but only Moscow or Saint-Petersburg, Russia
0 0 [Posted by: Oleg Artamonov  | Date: 06/08/09 10:59:46 AM]
Thanks for sharing your insights. I will have to look into these tools, I haven't got seriously into my own designs for a few too many years, and the tech is ripeer than ever now.

0 0 [Posted by: Crisspy  | Date: 06/10/09 02:38:49 PM]

Great article. Can you talk a little about the test system's calibration, accuracy and repeatability so there is a baseline?

I noticed the Hall effect sensor data sheet shows a Total output error of 1.5% (typ)at TA = 25°C and then the graph for mean total output error over temp shows about 3% at 25C and then falling off to under 2% at high temp... Add in the uC's ADC nonlinearity and offset/gain error of the analog gain stage and you might see 2-4% offsets/error in the results. Again, not a big deal, but it'd be nice to know and might just be a one-line statement with any future articles.

Thanks again.
0 0 [Posted by: ca_steve  | Date: 06/08/09 03:31:35 PM]
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Each channel was calibrated at two points: zero load and 20 A load, at room temperature. Calibration was performed with programmable load (0-30 A), shunt resistor (75mV @ 20A) and Uni-Trend UT70D multimeter.ADCs are quite linear (0.5 LSB INL) and were calibrated for gain and offset. So theHall sensor is the biggest source of error with current measurements.Wattages are not measured, but calculated in assumption that PSUs' output voltages are exactly 3.0V, 5.0V and 12.0V. I'm using PSU with independent voltage regulation, so such assumption is acceptable. Furthermore, for our purposes there's no need in very high accuracy, even +/-5 % is enough, because it's obvious that no one will choose PSU with rated wattage exactly as the power consumption we measured. Repetability is very good, difference <0.1A on each channel.
0 0 [Posted by: Oleg Artamonov  | Date: 06/09/09 02:59:38 AM]
Thanks for the info. Glad to see the repeatability is so tight - that will be useful down the road when doing comparisons. On accuracy, my concern is not so much on the total power consumed and PSU selection, but that I expect you'll use this tool for future graphics card reviews and their power consumed. Just a nit on my part - this is a great setup.
0 0 [Posted by: ca_steve  | Date: 06/09/09 09:33:25 AM]

It's definitely an interesting article, device and software, however the assumptions that people are purchasing far greater power supplies (and more expensive) than they require, as well as manufactures "declare overstated specifications", I don't think is generally the case.
Most people I know get the general power requirements from the product manufacturers.
min req. from EVGA:
GTX 285 - 550w
GTX 295 - 680w.
The listed power requirements by the card producers fall right in line with the measurements that you Mr. Artamonov ultimately produce; allowing for a few extra drives, some overclocking and my USB powered coffee plate.
Manufacturer listed p/s req. seem to be about right.
btw, I believe that a real gaming computer running Crysis w DX10 at 1920 x 1200 will peak power draw greater than FurMark as Crysis will load both the CPU @ GPU quite intensely at times. It would be helpful if you gave some specific power draw data for a popular demand requirement such as this.
Thanks for your work, respectfully,
0 0 [Posted by: MonsterSound  | Date: 06/08/09 09:37:41 PM]
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I absolutely disagree. I tested using a similar method a few months ago. We were building a system for a client, designed for 3D modeling. The system was i7 920 @3.2, 12GB DDR3, 2x GTX275 stock. I tested with following methods: Crysis all max at 1680x1050, FurMark with heaviest settings (burn in test, all AA, etc.), Prime95 on all cores (both small and large FPU), and finally, Prime95 on 3 cores with small FPU and FurMark on the 4 core all max graphics. The power consumption was the highest in the latter case, followed by Crysis by itself. I don't remember exact numbers, but I think the difference was about 10%
0 0 [Posted by: sstass  | Date: 06/09/09 12:16:43 AM]
Interesting that you absolutely disagree.
The statement was "No real game can load the computer as heavily as FurMark."
When I run Furmark Xtreme Burning Mode at 1680 x 1050 w 16x MSAA, cpu cores peak at 40%.
Running the same mode 16xMSAA at 1920 x 1200 and cpu cores peak at a lower ~30%.
Running even lower resolutions bring the core peaks even higher but less stress on the video card.
When Running Crysis at 1920 x 1200 w AA/AF, I get higher core peaks while the gpu is heavily stressed as well. These are my results.
0 0 [Posted by: MonsterSound  | Date: 06/09/09 01:03:44 PM]

Oleg, great article! Finally concrete results about power consumption.

I'm intrested, did you consider power efficiency curves? What about the idea, that efficiency is greatest at the half of maximum power? Although PC rarely works at peak long time, a bit of reserve power is good for general efficiency when PC is under normal load.
0 0 [Posted by: lsrdjan  | Date: 06/09/09 03:08:36 PM]

the software 'OCCT' and the tab 'power supply' does a better job of maxing out the psu power usage.
(by about 30-40 watt)

I before I used the perlin noise benchmark in 3dmark06, but the occt test is better at consuming power.

(but nothing works better than prime95 for finding an unstable overclocked computer..)
0 0 [Posted by: queuetrip  | Date: 06/09/09 06:20:01 PM]

The article measures some real-world systems that are extremely inefficient in performance/power and while a lot of real-world systems are like it would be better to have shown systems that are efficient at various levels of performance. For a person building a system, there is little reason not to choose the efficient mainstream components.

For example consider these systems:
High performance office/home/htpc/very light gaming systems more powerful for average uses than the article's home system and much more powerful than the office system, but with power consumptions of 35W idle and 65W full load. This is measured at wall including PSU ineffiency, so PSU output needed is sub 65W. A 3.5" drive should be used instead but will only increase power by a few watts.
0 0 [Posted by: CSMR  | Date: 06/10/09 12:34:38 PM]

I second the suggestion to try out some really high overclocks and then measure the power usage. I have always claimed that 750W is enough for almost everyone but people never listen to me.

I am personally running a 750W PC Power & Cooling PSU with the following hardware and overclocks:
QX9650 @ 3.825 ghz and 1700 fsb (will be pushed to 4.05 ghz and 1800 fsb this weekend)
4 gb ddr 1066 5-5-5-15 ram
2 x raptors
2 x 285 ocx's in sli
2 x optical drives
x-fi elite pro
0 0 [Posted by: digitalrurouni  | Date: 06/11/09 05:22:02 AM]

A very interesting article, I've learned quite a lot too, thank you.
0 0 [Posted by: GFC  | Date: 06/11/09 09:16:21 AM]

An exceptional article, that any computer builder should read.
0 0 [Posted by: tantryl  | Date: 06/12/09 08:05:58 PM]

Are you considering rail power limits? I see about 40A on 12V in your last table. How many 500W power supplies do 40A on a 12 V rail? Zero? 650W PS? Some do, but how many do it on a single rail, or the one that is going to the gfx/GPUs? Not many.
0 0 [Posted by: 40th Floor  | Date: 06/17/09 03:38:21 AM]
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Corsair VX550 — 41A@12V
Corsair HX520 — 40A@12V
Tt Purepower RX 550 — 41A@12V
Antec NeoPower 550 — 42A@12V
Enermax PRO82+ 525 — 40A@12V
0 0 [Posted by: Oleg Artamonov  | Date: 06/18/09 02:50:04 AM]

40th floor, I don't see why that should impose a problem. Even on split rail PSUs (say one with several 20A rails), the power for the graphics card will be divided across rails, it won't be limited to coming off one single one.
0 0 [Posted by: Joe Public  | Date: 06/18/09 09:08:56 AM]

Hey Oleg, nice job and great detail ... I just built one channel similar to your setup and used it to measure the 12 VDC on the CPU of an old sysetm (I used the ACS713 that you used). Even uncalibrated, I measured the CPU power of a QX6700 within a Watt or two of your CPU measurements (published in prior articles).

I am finishing up gathering parts to finish out a full 8 channel setup and am excited to see the results.

What is your background? -- Xbit's power data and info always seems to be spot on and your methods a cut above any other site.

Thanks again for the info, nicely documented methods (i.e. reproducible), and the wonderful idea -- beats a shunt (hands down) for data collecting and ease.

0 0 [Posted by: jumpingjack  | Date: 06/25/09 12:05:30 AM]


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