Jul
14
Written by:
George Ou
7/14/2008 2:56 AM
Update 8/20/2008 - I need to fix my mistake because I quoted some initial informal numbers from Jack that didn't include the 3.5" HDD or dual-threaded tests. Now that the I have his full data set, I'm need to make some corrections. I apologize for my mistake and I will fix it below, but my insistance that Tomshardware is off by a LOT has not changed though I was wrong about saying the Intel 945GC/Atom board could run on 802.3af. Tomshardware on the other hand only did NOT correct the mistake despite acknowledging my emails to them, they went ahead and and published more results using an 850W power supply which is horrendously stupid.
For those who are going to say that Thorn who critized me in the comment section was right all along despite the fact that he did not run ANY tests, he was still wrong by a long shot because he insisted that the Tomshardware numbers aren't that far off. It turns out that Toms hardware was off by 25.6W from the Sparkle 220W power supply and my hasty post based on informal data that mistakenly excluded the hard drives was off by 11 W. Let this be a lesson to me for posting informal data and once again, I apologize to my readers for my mistake.
After praising Tomshardware for doing a good job fixing their flash storage efficiency article, I must point out that Tomshardware's made another horrendous error by claiming that and Intel D945GCLF system with an Intel Atom 1.6 GHz processor consumes 59W idle power. Mr. Dandumont who authored the article claims that he used an "80 Plus" power supply implying that he was getting at least 80% efficiency on the PSU (Power Supply Unit) but that is a huge mistake.
UPDATE 7/21/2008 - Tomshardware's Senior Editor Matthieu Lamelot has responded that they used the Tagan EasyCon U15 530 W power supply. My 600W guess was fairly close and it means that Tomshardware loaded their PSU to roughly 3.6% load and that translates to roughly 30% efficiency which makes their benchmarks very inaccurate and misleading. Tomshardware should at least test with a good 80 Plus 220W PSU but ideally they should test with a sub-100W PicoPSU.
The 80 Plus rating only claims greater than 80% efficiency if you're talking about workloads between 20% to 100% output power and my guess is that Mr. Dandumont used a 600+ watt PSU which means he was likely loading the system at less than 3% workload. 3% workload on a PSU translates to a horrendous efficiency of less than 30%.
Tomshardware claims that the same system with a 7200 RPM 3.5" hard drive consumes 59W idle and 62W peak using an energy efficient power supply but this isn't even in the ballpark in terms of accuracy. Tomshardware needs to correct this error and start using some more appropriate and smaller power supplies for testing computers that draw less than 50 watts of output power.
Update 8/20/2008 - My PhD friend Jack who is a very knowledgeable and meticulous tester tested the Intel D945GCLF with a Sparkle SPI220LE 220W PSU and got a measurement of 34W idle and 36.4W peak input power consumption. Since the "80 Plus" SPI220LE gets around 73% efficiency at 19.2W output load according to Silent PC Review, we can reasonably estimate at 75% efficiency that the entire system actually consumes ~27W output power from the PSU.
Without the hard drive, the system peaked at 27.2W which means the output power from the PSU would be ~20W which is too much for 802.2af PoE. The Intel 945GC chipset is unfortunately a bit power hungry so when the next version of Atom with on-die controller and graphics built in to the CPU, we can hopefully see the output power requirement dive down below 10W but until then, 802.3af is out of the question.
The SPI220LE is above 80% efficiency when the output load level is above 20% and here we're only at around 8.1% load level so the efficiency drops. I've done some testing with the Sparkle 55W Open Frame PSU and found that it runs at around 80% efficiency for the Intel 945GC/Atom board despite the fact that it's not 80 Plus certified. This is because the 55W PSU is running at optimum load levels.
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44 comments so far...
Intel and Slander?
I wonder what the folks at Intel would have to say about this slanderous article produced by Tom's?
Thank you for again attacking Tom's Hardware and showing how they continue to lose relevance in the tech world. I used to be one of their faithful followers back in the Pentium II days, but am now finding out that they are simply not reliable as a information source anymore.
By nuCrash on
7/14/2008 6:40 AM
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Well, it's not slander or libel when it's incompetence
Well, it's not slander or libel when it's incompetence. This doesn't look deliberate; just incompetent.
By host on
7/14/2008 11:19 AM
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Re: Tomshardware botches Intel Atom energy efficiency tests badly
Hi George,
Congratulations about getting the SSD vs HDD comparison right from Tomshardware. You are and have always been a myth-buster of technology and are so good. After hearing that you are leaving ZDNet, I really had to follow you via Google and have been glad to see that you are still active in writing tech blogs as before.
I realized from your article that putting a more powerful power supply than what is really needed may not always be a good idea because of efficiency loss. I am building a system with Intel Core2Quad Q6600 processor, two 500GB harddrives, EVGA 8500GT nVidia graphics card, SLI-capable mother board (Abit Fatal1ty IN-9), and other usual stuff like DVD-RW drives etc. Can you provide some inputs on how much power supply do I really need? I am using Antec EarthWatts 500W.
Also, I have wondered for some time what is the cost/benefit relationship for efficiency in the long run. For example, a processor with higher power-to-performance ratio may be cheaper but would consune more power and may turn out to be costlier in the long run. Are you familiar with any study along these lines.
Thanks - Alok
By Alok on
7/14/2008 12:02 PM
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Q6600 and is slightly more power hungry
The Q6600 and is slightly more power hungry and it's an older 65nm technology. You might want to spend a little more money on the Q9300 45nm quad-core which has SSE4 which makes video encoding tasks much faster as well as other things. All Intel 45nm quad-core processors consume much lower power than Intel 65nm processors while being stressed by the average application.
The 8500GT is cheap and low power but it's not a good gamer and you might want to consider getting the 9600GT for a little more money. The 9600GT is good for gaming and uses fairly low power.
For the PSU, whether you do your parts or my recommendations, the SeaSonic 330W 80 Plus PSU is what I recommend. It's a very silent, reliable, and affordable PSU and it's more than enough power for what you're doing.
George Ou
By host on
7/14/2008 4:26 PM
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While their numbers may be off...
...the chipset's TDP is officially rated at 22W and the CPU's at 4W. Adding your 9W for the hard drive, 3W for a single DDR2 DIMM and approximately 2W for the fan and VRM inefficiency, I'd end up with a full load power consumption of around 54W at 73% PSU efficiency. From that perspective your numbers don't look any more realistic than Tom's Hardware's.
By Thorn on
7/18/2008 12:09 PM
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Thorn, Jack and I both MEASURED the numbers
Thorn, Jack and I both MEASURED the numbers. Jack measured a peak power of just 25.4 watts for the ENTIRE system including a 9-watt 3.5" 7200 RPM hard drive. It's quite silly of you to go spouting off theoretical numbers of 54W by adding TDPs when you've never done any measurements. For you to criticize our measured numbers with your theoretical numbers is laughable.
Tomshardware at least measured the numbers but they used the wrong power supply that resulted in less than 30% PSU efficiency. The idea that an Atom system would consume more than 50 watts is ludicrous. I've built dual-core Intel Core 2 systems with "65W TDP" CPUs where the entire system consumes less than 50 watts. http://blogs.zdnet.com/Ou/?p=934
George Ou
By host on
7/18/2008 12:16 PM
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I would expect the engineers to know their product well
I don't think it's silly to question a result that concludes a peak power consumption of around 7W for the CPU and chipset only (taking your numbers and deducting 3W for RAM, VRM and fan, which is conservative) while the actual manufacturer advertises a 26W TDP for those components and the engineers decided to put a rather large heatsink with active cooling on the chipset. Why should they waste money and marketing potential like that?
After all your criticism on Tom's Hardware's results is also just based on the guess that their results suffer from horrible PSU efficiency.
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