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480gtx sli power usage.

DooMeR

DooMeR

DooMeR

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Helllllo :)

I am planing to get a 480 gtx next week the gigabyte specail edtion one, it will be also be paried with a sandy bridge system

this is the psu i bought last week
http://www.overclockers.co.uk/showproduct.php?prodid=CA-116-AN&groupid=701&catid=123&subcat=1088

A good psu i think but will i be able to get away using that with a extra 480 gtx which a plan to buy at a later date.

My other psu is a Tagan BZ-900 powers my other system which ucuk no longer stock but heres the specs and i think its about 2 years old now.

specs can be found here

http://www.hardwarecanucks.com/imagehosting/24047e07b9a34e57.jpg


Which one would i be better off using i am pretty clueless when it comes to psu's but i think 750 watts will be really pushing it for 2 480gtx's yet theres a few people saying on interwebs 750 would be enough.

So some help is greatly needed, thanks for your time.
 
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I would have thought 750w would be enough, as running two GTX480s at load consumes around 620w. However, once a cpu/overclock is added the unit itself would probably running quite close to the margins, and it appears that the antec new truepower PSUs suffer from a small amount of voltage droop when close to it's max load capacity. It's not the end of the world, but may reduce the lifespan of the PSU/components in your computer.

Personally, I'd get a more powerful model just for peace of mind, but that's probably because I've had one go on me before. Completely up to you!
 
I run 2 x 470's, power use at idle is 280w, in game 530w, i ran furmark and prime95 at the same time, 866w and climbing, psu is a corsair hx 850w, not something id reccomend tbh.
 
Guru3D have 2x480's and an overclocked 6 core processor at around 700 watts.

You might get away with it but a 750W PSU will be running towards 100% capacity.

I'd use the Tagan. It has the necessary 2x6 pin PCI-E and 2x8pin PCI-E connectors.

If you're going for SLI make sure you get an SLI certified motherboard. Not all Sandybridge motherboards can do SLI.
 
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Thanks for the advice guys.

I looked into it more and you are all right 750 would be very borderline. According to the site i found they benchmarked crysis and total power consumption is 668 watts in sli.

In future mark It is 851 watts. So i could properly get away with it but its not really worth the risk when i got a 900 watt psu even thoughs its 2 years old :)
 
With capacitor aging thrown in if you've been using your 900w Targan heavily it is probably sourcing about 720w now. While the Antec is still at 750w.

Capacitor aging is a nonlinear curve so after about 2 years it normally flattens out. You're not likely to lose any more power, but as it stands it's possible your Antec is better suited to the job.

just make sure you dont run something like Furmark. They probably have overcurrent protection, but you still don't want to risk overloading either PSU


Btw looking at that link the Targan also says "maximum power: 900w". This might be a shady way of saying it can spike upto 900w for impulse trains and may be incapable of providing sustained 900w. In which case it would be all the worse compared to your Antec. Try looking up a review on it and see if they load tested it upto 900w. Not a lot of people load test high power PSUs because a lot of reviewers dont have the right equipment for it-- the kind of stuff you'd normally found in a power lab and usually very pricey.
 
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layte said:
Just going leave this here.... http://homepages.nildram.co.uk/~layte/pics/IMAG0046.jpg
Click to expand...



Don't forget that power draw from mains does not equal power output of the PSU, because these PSUs are about 80% efficient, and also because power draw from the AC mains may have a significant complex power (expressed as a complex variable) of which there is real power (the real part) and reactive power (the imaginary part). (This is also why UPS are normally rated at VA and not Watts, because by definition Watts is only applied as a measure of real power). However, the power output of the PSU is DC and therefore entirely real power.

Though, to be fair, power meters also normally will measure only real power (Vm x Im x Cosø) and give a reading from that. PSUs normally apply apply about 0.99% power factor correction (to bring the VI lead-lag in phase), but still what you're ending up with is a different in input AC power (real + imaginary power) and different output.

So don't get carried away with power draw from the AC mains as an indicator of the size of PSU you need. A common mistake oft committed by those not versed in electrical engineering/power.
 
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And I thought my Seasonic 850W was good enough for my overclocked i7 and two overclocked gtx470's..........it wasn't :(

If running everything at stock you will be fine. If overclocking, get a decent brand 1000W at least.

I got a 1200W as a replacement (just to be on the safe side)
 
Greebo said:
And I thought my Seasonic 850W was good enough for my overclocked i7 and two overclocked gtx470's..........it wasn't :(

If running everything at stock you will be fine. If overclocking, get a decent brand 1000W at least.

I got a 1200W as a replacement (just to be on the safe side)
Click to expand...
I thought about moving to a 1000w unit myself, but i suspect the hx850w should be fine for my setup, only run the cards on a mild oc of 750mhz and will avoid running crazy apps like furmark.:D
 
Yeah forget that furmark/OCCT crap. artifacting under those is meaningless as the card is generating way more heat under those and drawing way more current. Even if it artifacts it doesnt mean your card isn't stable at normal temps

then again, with a DX11 card you may not artifact at all under furmark and find that it crashes the moment you run a DX11 app

Best to load couple of cores with prime and run Crysis or Heaven or something to see if it's stable
 
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