Power consumption..

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ajf

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I have read a lot about newer systems requiring anything upto 1kw power supplies.
I bought a 520w one for my new system and initially the shop said that may not be enough.
Out of interest I purchased a plug in power meter that registers current power consumption.
Even when running a game or Prime95 etc it never gets over 230w to 240w.

So, what sort of systems really require 600w, or even 1kw power supplies?
 
There is definitely something to be said for running a PSU significantly below its maximum capability. I certainly wouldn't want my Hiper-R pulling anything like its full 580W rating... especially with their reputation. :-)

It's like any device, if it's running flat out then it's unlikely to last. And electronics are no different to mechanical devices in that respect. You might not be able to see the stuff that's moving, but all that heat's not being generated by infra red fairies! :-)

So I'd always want a few 100W of head room these days. However I think there's a lot of truth in the idea that an awful lot of high power PSUs get sold to people who have no real idea what they need. Of course you can never be sure what you'll need for the *next* upgrade, so it's easy to get sucked into a 'just in case' scenario. But the way elecricity prices are set to rise in the future (and they certainly will, sadly) we should probably all be paying more attention to the bang for buck our systems deliver*.

Andrew McP

*Says the man who just got drawn into three-screen gaming. :-) In my defence, I'm looking at 3 x 1280x1024 monitors drawing 35-40W each. But the 19" CRT on my gaming box is rated at about 120W, so the only increase in power will come from the beefier vid card I'll eventually pick up.
 
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I'd largely agree with Andrew McP that there is no harm in having spare capacity even if it isn't strictly needed, however there is a definite efficiency band for PSUs where they work at their optimum so say between 50% and 80% of their maximum they are at their best - much above or below that and they start to become less efficent.

Remember also that not all PSUs are created equal, one from a decent brand is much more likely to be able to supply the rated voltage than some cheap brand e.g. a Q-Tek 600w PSU might actually only be able to supply 400w continuous.
 
ajf said:
I bought a 520w one for my new system and initially the shop said that may not be enough
Click to expand...
Unless an el-chepo unknown brand, typical store BS :mad:

Lots of factors to consider when looking at PSUs. But quite a number are advertised at peak wattage hence why x brand 520W PSU won't be as good as y brand one. The trick is to look at the prices. But pays also to do your research on the interweb :)
 
ajf said:
I have read a lot about newer systems requiring anything upto 1kw power supplies.
I bought a 520w one for my new system and initially the shop said that may not be enough.
Out of interest I purchased a plug in power meter that registers current power consumption.
Even when running a game or Prime95 etc it never gets over 230w to 240w.

So, what sort of systems really require 600w, or even 1kw power supplies?
Click to expand...

Don't forget, PSU's have an efficiency of around 80% max so when the wall meter is reading 240W, Your PSU output is less than 200W

AD
 
Well I'm running my sig machine off an old Arctic Cooling silentium case, with a built-in 350W PSU - yeah its probably running close to max effort ;-)

It's rated to 450W peak output, keep meaning to get a power meter to see what its actually using, just seems to swallow every upgrade with ease TBH!

Doubt it'd do dual GFX cards though.
 
Andrew_McP said:
I think there's a lot of truth in the idea that an awful lot of high power PSUs get sold to people who have no real idea what they need. Of course you can never be sure what you'll need for the *next* upgrade, so it's easy to get sucked into a 'just in case' scenario.
Click to expand...


i fell into that catogory when i got my PSU, brought a FSP sparkle 700W when i could have gotten away with a cheaper PSU, however with hindsight i see it as a good purchase as it meant that i havent needed to change PSUs for a few years and it is proven itself capable of coping with the changes i made to my pc since i brought it (sktA 2800xp, 9800SE, 768MB ram to [email protected], 4870, x800XT, 4x1gb RAM)
 
MeatLoaf said:
I dare say a quad SLI system may need a beefy PSU
Click to expand...
Yep, two quad SLI PCs need one 1.1kW PSU
http://www.overclockersclub.com/reviews/computex2008/images/311.htm


semi-pro waster said:
cheap brand e.g. a Q-Tek 600w PSU might actually only be able to supply 400w continuous.
Click to expand...
More like 350 before turning to fireworks:
Go to that "not exactly hexagonal" site and add this to end of url: content/item.php?item=1359&page=19
And in time it will probably blow up even with lower load.

300W is general limit for junks:
http://www.jonnyguru.com/modules.php?name=NDReviews&file=print&reid=71


Andrew_McP said:
So I'd always want a few 100W of head room these days.
Click to expand...
Watts are absolute so it's better to size PSU so that combined peak draw of components would stay around 70% of output capability.
Also taking care of case cooling is important part...
You wouldn't expect electronics to run well in 100C sauna, or would you?
 
Just thought I'd re-visit this thread after buying a cheap (but seemingly reliable based on testing known wattage devices) power meter.

My game box: E6600@3GHz, 2Gb RAM, 1 x 250Gb HD, assorted fans, 8800GTS 320Mb. The meter was only connected to the lead connected to the PSU. Additional power will obviously be drawn for the monitor and independently connected peripherals.

When switched off (but the PSU turned on) the system draws about 9W.

Peak at boot: 196W
Idle in deskstop: 165W
Crysis menu: 247W
Peak in Crysis gameplay (high settings, x4fsaa, 1280x1024): 258W
I did try higher resolution in Crysis, but all that happened was the frame rate went down. No more power was drawn.

However Crysis uses the vid card more than CPU, so...

Desktop + Orthos (dual core in use): 223W
Desktop + Furmark (x16 fsaa, 1280, low frame rate) : 275W
Desktop + Orthos + Furmark: 314W

That 314W was the highest reading I could get on the power meter, and it's fair to assume nothing's going to be able to beat that for stressing the PC. Even allowing for a very conservative +/- 10% for accuracy, that gives me a fairly decent amount of headroom if I upgrade the vid card. After all, the older 8800 cards weren't as efficient as the later cards.

Hope others find that as interesting as I did.

Andrew McP
 
You aint gunna be playin crysis while cpu stress testing in the background so as you illustrate above you dont really need to add up every components top power draw.
 
Hi Andrew,

I did exactly the same some time ago and found pretty much the same thing with my system.

With overvolting on the RAM, CPU and vidcard (hardmod), I think I was able to push 370 Watts.

Given 80% efficieny, that's 296 Watts actual.

That's why I'm still using the OCZ 520 Watt in my sig and have no plans to change it unless they release 90%+ efficiency power supplies.

I LOL when I see people using kW PSUs. (Unless they have 4-way SLI or something...)

Great article here:

http://www.techreport.com/articles.x/15208/13
 
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Jimbo Mahoney said:
Great article here:

http://www.techreport.com/articles.x/15208/13
Click to expand...

Interesting, thanks.

I can understand how people get lured into the bigger PSUs. After all, it's the most important bit of a PC really. But I do think the last few years have had the fingerprints of <spooky music>Marketing Departments</spooky music> all over them.

Mind you, what hasn't! We all fall victim to it at some point, no matter how careful.

Andrew McP
 
Sorry, I completely forgot I had posted this thread!
Some interesting comments and I will also read the links, but as I thought it does seem in many cases 'bigger is better' syndrome :) lol
Some interesting figures from your test andrew mcp. I wil double check the accuracy of my meter as I know my readings were quite a bit lower, especially for tick over and boot etc.

Andrew
 
I can understand how people get lured into the bigger PSUs. After all, it's the most important bit of a PC really. But I do think the last few years have had the fingerprints of <spooky music>Marketing Departments</spooky music> all over them.
Click to expand...
Well, consider this, your very average single card system (you don't even have a quad in there) draws around 200 under full load at the wall and it is never a good idea to top out a PSU (it increases strain, operating temperature and noise (and reduces lifetime of the PSU).

You can find testing graphs on operating temperature and fan noise for most big name PSUs and around 50% load it can start to get toasty. Many, even big-name brands use cheap caps that are abnormally sensitive to temperature (PSUs are often rated at 25C which is ridiculous for a gaming rig) and it is also rare to have the entire rated power available over the +12v rails (the Corsair HX520 has approx 480 Watts).

It is true that 1000 Watt for a single card rig is ridiculous but you also have to watch under-estimating requirements. Quality 500 is plenty for single card rigs but going much under that makes me uncomfortable about long-term longevity.
 
Well I bought my 1kw psu for the same reason I bought my 480w psu, four years ago - longevity.

The 480w was overkill for the athlon 1.4, single hard drive, single cd writer, x800xt. However, I upgrade and add to my system on a regular basis.

The final straw for my 480w psu last month was adding a bluray writer. Not enough power anymore.

psu's lose a certain percentage of their power output each year as well (10% from memory).

So maybe I was only pulling 400W with all the stuff inside my pc, however I wanted room to grow without having to worry about changing the psu again in a year of so time.

I may want to add a 2nd card (new mobo of course) in the next year and god knows what else.

So at the moment my 1kw supply may be running at only around 50% capacity but that means the fan hard moves on it and its quiet.

So people may think I am mad but hopefully I will have more tha enough power for the next 4-5 years.

If I had just bought a 300W psu 4 years ago I would have had to change it at least a year or two ago.
 
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