Power Supplies

[TriEclipse]

See bottom of post for links to more information in this thread.

Lets talk about how much power AN ENTIRE 8800GTX SYSTEM consumes.

Clicking on this link will take you to a DailyTech article exploring the 8800GTX. In this review, they will also look at how much power an 8800GTX consumes. Look near the bottom, that's where you will find the power consumption. You will also find these specs;

* Intel Core 2 Extreme QX6700
* NVIDIA nForce 650i SLI based motherboard
* 2x1GB PC2-6400
* NVIDIA GeForce 8800GTX
* Western Digital Raptor 150

Now note this; Incase you didn't read the article, they mention that the power being measured is from the wall, meaning that the actual power supplied to the components is less, after factoring in the PSU efficiency. They are using a Power Supply that has an efficiency rating of 85% (excellent). And incase anyone's curious, they're using a Kill-A-Watt power meter to measure the power that their system's pulling in (again, from the wall).

That means that while they are measuring 321W out of the wall for the entire system, the actual power that the system is pulling in is (321W x .85) = ~273 W. 273W power consumption for a system with a Quad Core processor, high-end motherboard, 2 Gigs of RAM, an 8800GTX, and a WD Raptor.

Seem low? It should. But not because it's inaccurate, it's because everyone sees the huge Power Supply numbers being put out by the PSU companies, and they think that they must immediately have a 700W or 850W Power Supply.

Now what kind of a Power Supply would you need to run this system with a 8800GTX? In a perfect world, you would need a Power Supply rated at 273W. Yes, the power supply would have to say [Name of Company] 273W. We can round that up to 300W for simplicity's sake.

But our world is far from perfect. Power Supplies should never be run at 100%, or even near 100% output. A simple example is when you turn your computer on. At that instant, every piece of hardware in your computer goes to it's max power consumption for a couple of seconds as it starts up. This max is higher than what your system shows even at load. So if your PSU can't supply that -- Your computer can't turn on. For example, CD drives draw ~1A from the +5v and +12v rails, and hard drives may get up to 1A on each of those as well. While that may not sound like much, each of those components can more than double that draw on spinup. Thus, if you have too many of either component, you computer may not be able to POST with an inadequate PSU. Also, Power Supplies get hot, and that heat leads to deterioration over time. As if that wasn't enough, you will leave yourself absolutely no room for upgrading. So getting a power supply near the max of your load power consumption: Bad.

Besides that, many other "bad things" can happen to PSUs that would take a few more paragraphs to list. PM me if you want to learn more (and make your eyes bleed from reading). Its normally a good idea to leave a decent amount of breathing room for your PC and some more overhead as PSUs deteriorate over time.

Also, all power supplies are not made equal. While Watts are a nice indication of a Power Supply, it's the Amps that are most important. Especially the amps on the +12v rail.

So...what kind of PSU would be needed to power a system with an 8800GTX? A Forton 400W PSU with 34A on the +12v rails (it has 2 rails) is a good choice. 34A means that it can supply 408W on it's +12v rails, although the actual output is less than the sum of the two rails. But a Power Supply that has more Watts being supplied on it's +12v rails than the entire PSU can is an indication of an EXCELLENT Power Supply. For an 8800GTX system like the one above, this Power Supply would be running at 68% load, and gives you an overhead of almost 50%. It doesn't get much better than that.

Someone disputed that a 550W PSU wouldn't be enough for an 8800GTX system. Fact is, that a 550W PSU would be quite overkill, but I wouldn't argue if someone wanted to get it to leave room open for some [pretty hefty] future upgrade. A 550W PSU would give you an overhead of about 100%.

Hope this will keep people from wasting money on 700W PSUs when their system actually needs less than 250W. Questions are welcome.

Continued
Continued 2
Why Watts Don't Mean Jack

[TriEclipse]

Originally posted by fade2black2004
im still glad i got my 650watt antec psu. now i dont have to worry about upgrading for a year or so

Remember that people aren't about to pay $150/month in electric bills for their computers anytime in the next decade. The goal of hardware builders isn't just to make faster products and to not care about how much power they consume - Hardware companies also try to minimize the amount of power that they consume.

As an example, future Dual Core Intel processors based on the 45nm manufacturing process are expected to consume 57W, and AMD's K8L Dual Cores are supposed to range anywhere from 35 to 89W, depending on the clockspeed. This is down from the minimum 65W that Core 2s consume right now, and the 80-something Watts that Athlon 64 X2s consume. So its not like power consumption is going to keep increasing forever and never be stopped.

Just an example of power consumption actually reducing over time. So it might very well be the case that even 650W will never even come close to being fully used, and you could've done with a much smaller PSU. A 500W PSU still leaves quite a bit of room for any future upgrades; Also note that any "upgrades" to the amount of power an 8800GTX consumes would have to come in the form of ridiculously impractical hardware (such as 4x4).

Originally posted by RalliArt882
I have an OCZ GameXStream 700W too. There's no reason to have regret though, we buy those because we know they will handle things years from now and they won't go out on us. If there is ANYTHING you shouldn't compromise, it better be your PSU. Because if it goes out, you can bet a couple more things will go out with it.

Power Supplies failing is something that has to do with the quality of the PSU, not the amount of energy that it supplies. A high-quality PSU that supplies a low amount of watts is still a better choice than a low-quality PSU that supplies a large amount of watts. OCZ is an excellent PSU maker, so I can't really argue against that, but the 400W Forton is still less likely to fail than the 700W OCZ.

By the way, 72Amps on the +12v rails is so much overkill...Half that would be enough to keep a system going for a LONG time (years). Just an example of spending more money than needed.

Originally posted by fangs2000
I REALLY needed this post. I have been using power supply calculators to work out how much my new build would require, and always thought it was off. Looking around everyone seems to say "You need at least 500W PSU to run XYZ", now it seems the calculator is correct. I will probably look into downgrading my PSU in that case, maybe going for a 400W one. I cannot see the point of going SLI/XFIRE, nor quad core. I also never cared for the high-speed hard drives. I am happy with a 7200RPM one.

I have a question though, Is there a chart rating the quality of different companies? I have seen some REALLY cheap PSUs (example, Sansun 450W for 24.99, or Ebuyer Value 550W for £21.99) . I am a big fan of reliablity over performance.

Again, thanks for this post.

Don't use those calculators as a measure of how much power your system is consuming, but as an example of the power supply that you should get. And still, Power Supplies are not made equal, so the 450W required in a PSU that it shows could be the same thing as a good 400W PSU or a 500W crappy PSU. As long as you stick with good brands, and don't go below 400W, you should be just fine in any non-SLI system.

Which leads me into answering your question. Sorry to say that there is no real list of good PSU companies. Any sort of list that exists is only a collection of what other people think are good companies. That kind of a list is completely useless since only one person needs to think that a known bad company is good, for it to be included in such a list. I've seen it happen too many times.

The only real way to know which PSU makers are good is to hang around places that discuss such things. The Power Supplies subforum over at [H]Forums is one of my favorite hangouts. You'll have to be there for a decent amount of time to be able to sift through the crappy ones and the good ones though. That, or you could just ask us which ones we think are good, for what its worth.

As for the PSUs you listed, I wouldn't touch either of those with a 10-foot power cable. Just because the 400W Forton is cheap doesn't mean that all cheap PSUs are good. Infact, that Forton is an extreme rarity. The way you tell a good PSU is from it's maker, and brands such as Forton, Antec, PCP&C, OCZ, Hiper, Seasonic, etc are some good names off the top of my head.

[nitestick]

stickied

no more of the unrelated posts like there were in the original thread.....speaking of which i'm going to go clean that up. good work

[baronvongogo]

wow nice thread, I myself had told others to get 550W PSU`s for an 8800GTX. I love being proved wrong its a lesson learned well done.

Also I think all sticky threads should be made a golden colour to make them stand out they are easy to overlook

[Tkey]

Nice , well done

[nitestick]

ok post has been patched up now, the edit is in place and i shifted the post from the other thread.

[TriEclipse]

I love how perfect the timing of this was.

L'inq - Ultimate Overclocked PC only needs 500W Power Supply.

Originally Posted by The Inquirer
Yes, after over 2 days of running heavy stuff in this overloaded (700W++ class!) system config, the 500W MGE power supply is still alive and well. I spent quite a bit of time monitoring its LCD display power spike reports, and the highest one was 429 Watts, consumed during the full 3DMark06 run (Proxyon landing at UXGA 4xAA anisotropic filtering). I managed to take a quick blurred shot of one 423 Watt screen for your viewing pleasure. In the 'typical' use (i.e. running the Ntune utility and opening up a PDF file) it was at about 315 W, and it went up to nearly 330 W when running Sandra benchmarks.

Of course, the argument still stands that there should be a reserve, for unexpected power usage spikes - and I agree. The only thing is, I believe that the heaviest runs of multithreaded, hi-res 3DMark06 are a kind of power usage spike, naturally - they stress pretty much everything, from the CPU cores, their caches, FSB, memory, PCI-E, also 25% overclocked via auto LinkBoost, graphics cards, the power-consuming water cooler, HDD, just not touching the DVD. Yes, a 600 W PSU would give me a more peaceful sleep here, but it is obviously not a necessity. The Ultimate PC config of today, plus or minus few trinkets can be, even in heavy use, reliably fed by a top-class 500W PSU, at least for 2 days non stop.

Yeah, she only ran it for 2 days on that setup, but I wanted to mainly focus on how much power the system consumed; 429W for more hardware than I wish to list again. I'd prefer more of a 600W quality PSU to run it, 429W is still too close to 500W for my tastes. Its certainly feasible, using a 500W PSU, but the quality of your PSU would deteriorate quicker over time.

[TriEclipse]

Just another addition to the thread.

Why Watts Don't Mean Jack.

The wattage of a PSU is a lame way to measure the actual output of a PSU. The total wattage given is the sum of all of the rails on a PSU added up (+3.3V, +5V, +12V1, +12V2, -12V, +5VSB). The way PSU companies will trick you, is by bumping up the Amps on the red rails. These rails are relatively minor, and don't really provide power to any of the major components of your system. However, they still count towards the total power output of the PSU, and this can skewer the numbers. The blue rails, are the important ones. The +12v rails are the ones that provide most of the power to the major parts in your system. The more Amps on this rail, the more power will be supplied to your system.

Example; 400W Forton PSU and 580W Hiper. Both are excellent PSU makers. Look at this;

Forton - +3.3V@22A, +5V@21A, +12V1@18A, +12V2@16A, -12V@0.3A, +5VSB@2A.

Hiper - +3.3V@30A, +5V@36A,+12V1@20A, +12V2@18A,-12V@0.8A, +5VSB@2.5A.

The 580W Hiper PSU has 4Amps more on it's +12v rails than the Forton does. Is 4Amps worth the difference of 180W? Don't make me laugh. So that would mean that this Forton that has been "labeled" 400W is near equal in power to a 580W PSU. Wattage doesn't mean jack.

[iUser]

Thanks for all of the information! I am actually starting to learn about custom building computers and I was planning on going with an 8800 GTX. I was going to buy a 650W power source because I had read it in a magazine, but thankfully you just saved me some money!

[TriEclipse]

No Problem. Yeah, 90% of PSU reviews are fa;se because while the reviewer may have above-average computer knowledge (average in this case being the average hardware enthusiast), their knowledge of electronics isn't quite up to par. Most of them will say something along the lines of, "I used this PSU with this hardware, and it worked," without mentioning much else. They end up doing more harm than good, as they occasionally recommend units that are clearly faulty. My problem, though, is with the ones that recommend PSUs that are way over the top.