Debunking Power Supply Myths
by Christoph Katzer on September 22, 2008 3:00 AM EST- Posted in
- Cases/Cooling/PSUs
PSUs for High-End Systems
Even though our high-end system consumes more power, we used the same graph layout. That means the resulting graphs stop at 600W, despite the high-end PSUs all being capable of providing more power than that. Our high-end system sports an SLI setup using two NVIDIA 8800 ultra cards; 3-way SLI would be a bit more demanding, but we don't feel it's a good indication of what people are actually running. The third card would also only add another 50W to 90W of power consumption to our system, since the third card is rarely taxed as much as the first GPU.
- Antec NeoPower Blue (650W) actively cooled
- Antec Signature (850W) actively cooled
- Silverstone Decathlon (700W) actively cooled
- Zalman ZM850HP (850W) actively cooled
- Enermax Pro82+ (625W) actively cooled
We've included the Enermax Pro82+ 625W from the midrange selection as well. Again, efficiency is not the major issue when it comes to choosing between these products. The two lowest rated power supplies -- Antec NeoPower 650W and Enermax Pro82+ 625W -- are less efficient over the tested range, but that's expected. The results all of her around 85% to 87% mark, and one or 2% difference really isn't going to matter much. Still, the Zalman and Antec 850W units place at the top of this chart.
Again, the two power supplies with the lowest output rating perform worse in this test, generating much more noise than the competition. The higher rated units don't have to work as hard, since they are running at a medium load. Those three PSUs remain very quiet along with providing better efficiency, making them the better for a high-end setup. The Zalman and Antec Signature 850W units would be our choice, if only for the extra headroom. Either PSU would have no difficulty with a 3-way GPU setup, provided you have sufficient PEG connections available. That brings up the next topic of discussion.
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computerfarmer - Tuesday, September 23, 2008 - link
Good article! Based on the number of comments, this has many of us thinking. This gives a way of figuring out our needs vs bigger is better.This article gives us enough information to make educated choices. Looking at the 12V rails is a good place to start along with total power. With a single 12V rail like Corsair VX series, the amount each rail carries is a non issue.
A rule I have always followed is to use a power supply with at least 20% more power than the maximum required.
dragosmp - Tuesday, September 23, 2008 - link
Hey, I just wanted to say that after posting this link on OCN, there were tenths of replies. People want to know how much various things consume, as all this 1kW PSU hype hype is getting very tiresome.I for one would be curious how did you measure the current thru the PCIe slot - have you modified the slot to access the power lines? Soldering geeks would really like to know :)
And lastly, browser compatibility. This comment is very hard to write in Chrome (writing overlapping), maybe you or google will fix this.
Cheers,
Dragosmp
Fudus - Tuesday, September 23, 2008 - link
I am stupid and run my 4850 off a 300W power supply, with a sata power>molex>pci-E power connection. Go Go overloading!It seems to work at stock speeds under stress as well for some reason. I really didn't expect it to work this well (C2D e6550, Radeon 4850,300W power supply, 2GB RAm, G33 motherboard, 1 HD/DVD+RW)
marc1000 - Tuesday, September 23, 2008 - link
you are not stupid, Fudus. if you sum the power for your c2d (never more than 65w), mobo (40w), ram+HD+DVD (5+15+10) you have 135w. then add the 4850 and you are still fine with a 300w PSU. Like i Said before, I have a 90W CPU (that old Pentium-D, argh!) but run a radeon 3850, so my system consumes about the same energy as yours. and the 300w is working fine with me too. or else I would be a stupid too =Pdragosmp - Tuesday, September 23, 2008 - link
Wow, this gives me hopes to mount a 4670 on a 120W pico-atx powered rig.How is the noise, the +12V level?
oopyseohs - Monday, September 22, 2008 - link
I have seen upwards of 700W while testing on old QuadFX systems with 8800Ultra SLI. I would imagine that Skulltrail overclocked to 4.0GHz (easy) and 2x Radeon HD4870X2's in CrossFireX would demand significantly more than 700W. Of course these systems are rare, but they do technically validate the "need" for power supplies that output 1000W+.In any case, thanks for this article. I think it does a great job of showing why ultra high-output power supplies are not even close to necessary for 99.9% of the computing world.
JarredWalton - Monday, September 22, 2008 - link
I have a Q6600 @ 3.42GHz with dual 3870 cards, and that peaks at around 650W at the outlet. Certainly there are plenty of overclocked PCs that can draw more than 700W... but once you take efficiency into account, my PC is only really using around 520W. I've also tested high-end water-cooled setups with 8800 GTX SLI that topped out at 650-700W power draw as well. I personally think with ultra high-end PSUs that having six 12V rails isn't very useful as well - some of the problems people experience with lesser PSUs simply comes from 12V rail distribution.If you're running dual GTX 280 cards and a quad-core (probably overclocked) CPU, I don't think there's anything wrong with 1000W PSUs. In fact, I know Gary has blown a few 1000W PSUs with his overclocking testing in the past. However, I'm running perfectly happy now with a 3.2GHz quad-core and really don't need even that much CPU performance; it's all about the GPU for games, and CPUs are only really taxed in 3D rendering and video encoding it seems.
Griswold - Monday, September 22, 2008 - link
Now that you made that clear, give us some of your great reviews for reasonably dimensioned PSUs instead of these 600-1000W bricks. :Pwhatthehey - Monday, September 22, 2008 - link
Maybe it's just me, but I sort of got the impression that the reason for this article is precisely that Anandtech is tired of only getting the highest-end power supplies for testing. It's all marketing BS of course: they don't want to limit sales of the $300 1000W PSUs so they only send those out for testing.Or maybe the truth is more nefarious: they figure if they send out a top-quality 1000W PSU that has great efficiency and voltage regulation, unsuspecting buyers will buy their lower wattage parts that might not be all that great? The first is more likely, but it wouldn't surprise me if some of the less expensive 400-500W PSUs (even from major brands) use much cheaper components. Which is why we all want to see them tested, and probably also why the companies don't want to send them out for review.
Martimus - Monday, September 22, 2008 - link
Since this article is about choosing a PSU for a new computer build, it would have been nice to include new components like the P45 chipset, or the new nVidia or AMD graphics cards. I started reading it with the hope of knowing how well the Antec Earthwatts 500W PSU that came with the Sonata III case I bought would be do with various build options. The problem was that with only old equipment being used, I couldn't come to any real conclusion. It seemed to read more like a report to prove a point rather than an actual guide written to help with a new computer build. I am not trying to berate the article, but I just don't see the point of it.