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-   -   PSUs: how much power do you really need? (http://www.hardwarecanucks.com/forum/reviews-articles-web/1183-psus-how-much-power-do-you-really-need.html)

Babrbarossa May 8, 2007 01:32 PM

PSUs: how much power do you really need?
Before you run out and buy that supercharged diesel generator to power you 8800GTX SLI computer, have a look at this article by Legion Hardware where they measured what a monster system really needs. They took 4HDs 2X8800GTX, quad core CPU, 6X120mm fans- you'll never guess what they came up with: 550W!!, and it's been running fine for two months.

Are you currently thinking of building an SLI enabled Nvidia GeForce 8800 GTX gaming system with an Intel quad-core processor and a couple of hard drives in RAID? Well if you are then you need a 1000 watt power supply right? Wrong, but how can this be wrong with so many 1000 watt power supplies becoming available! In fact you donít even need an 850 or 800 watt power supply to safely operate such a system. After recently building this exact system we discovered that the maximum power demand created by this configuration was just 530 watts. Basically we built an Intel Core 2 Extreme QX6700 system with SLI enabled Nvidia GeForce 8800 GTX graphics cards using the ASUS Striker Extreme motherboard and four Seagate 320GB hard drives. Along for the ride were four 1GB DDR2 memory modules and six 120mm case fans as well as a water-cooling system. Even with all this high-end hardware installed we were only able to generate a maximum power demand of 530 watts.

More from Legion

Patriote May 8, 2007 02:07 PM

Oh well. I guess my 750W will be more than enough for 2 R600s. Thats until it die...

JayDee May 8, 2007 02:28 PM

Cool Babrbarossa, that's good to know.

I bought a Corsair 620watt PSU for my new build and it's more than I need. But I hope that it's a PSU that will perform reliably for a long time and that's worth a little extra coin to me. I also put a UPS front end = I don't like power/PSU problems :ph34r:

sswilson May 8, 2007 02:52 PM

The issue isn't so much that a person needs a 750W+ psu to power a mega rig. It's that they need a psu that's able to put out clean continuous power with a good 25% overhead so that they aren't running their PSU full out 24/7.

Unfortunately most sub-$120 psus cannot do that no matter what the box says they are rated at.

b1lk1 May 8, 2007 02:52 PM

I have said this a few times, there is just no need for those giant power supplies except for some good ole E-Peen....

SKYMTL May 8, 2007 03:33 PM

Oh man does that article give people the wrong impression.

It is basically saying: well, just because this PSU is powering my system, it is doing so without any problems. Not once I did a see a mention of ripple or voltage regulation in that whole article and those are two things that are PARAMOUNT when choosing a power supply. If there is excess ripple (considering the quality of that unit and the amount of stress being put on it I'm sure there is) that person is probably damaging their components without even knowing it.

It is articles like this that leave me stunned how some people deem themselves fit to talk about products they don't know a bloody thing about. It actually really pisses me off.

Let's take this apart.


Even with all this high-end hardware installed we were only able to generate a maximum power demand of 530 watts.
How was this measured? There is no mention if they used a clamp meter on the PSU cables or a load detector (read: Kill-A-Watt, Power Angel, etc.) on the power plug itself. Nor was it mentioned what programs they used to put load on the system. Many people use background applications as they game and that is what I do in my PSU reviews. With my system (X2 3800+, SLI 8800GTS, 1HD, etc) I was able to draw 423W from the mains during my tests...they are completely flawed when determined that their system draws only 530W under extreme load.


What I can tell you so far is that most gamers will not build a system that uses more than 450 watts of power at full tilt. Therefore, they require no more than a 500 watt power supply!
:doh: :doh:
Are you kidding me? With 90% of that power being drawn from the +12V rails, many 500W PSUs have their 12V OCP circuits set as around 18A (216W). Now, a pair of 8800GTX cards draws about 300W under load so then right away, your OCP will trip and shut down your computer. Again, how this guy is SAFELY running what he lists is beyond me...


Currently the latest Intel Core 2 Duo and AMD Athlon64 X2 processors only consume 65 watts of power when at full load.
WRONG!!!! This is a common mistake of many rookies; they state the TDP of the chips rather than the actual power consumption. Truth be told, after doing countless tests and consulting many other sites, I have determined that the power consumption of the X2-series is between 78W (3800+) and 104W (5200+).
Source: NCIX FORUMS - Looking to buy a Power Supply? Look here...


Even with SLI 8800 GTX graphics cards, there is really no need to purchase anything greater than a 600 watt power supply.
A distinction MUST be made between quality and crappy PSUs. Just saying "Antec, OCZ, Thermaltake" means NOTHING as each of these manufacturers has massive differences in the quality of their PSUs.

There is so much more that I can say but I think it is enough to advise you guys to take this article with a serious grain of salt.

Babrbarossa May 8, 2007 10:40 PM

HAHA! Awesome SKY- That's what we pay you the big buks for, heh?:biggrin:

pscout May 9, 2007 12:16 AM

and don't forget the demands of oc'ing.

OC'ing the cpu not only needs stable power, but depending on how much extra volts you give it and how high an fsb, you can easily double the power draw. Even tho c2d's are much better than the prescotts, but they also OC a lot better so the total power draw can be nearly as high as a prescott under 100% load.

Ditto for gpu's.

And longevity under sustained loads ... i am a folder ...every rig is oc'ed and runs 100% load 724.

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