Power Supply for an i5 Sandybridge build?

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What Power Supply would you recommend for an i5 2500k Sandybridge build? Would a Corsair TX850 or 750 be okay? I was planning on having a mid range card in there like a GTX460. One HDD, a DVD±RW, Soundcard, will have a few usb devices connected max, two pci cards. Does 750 or 850w psu seem about right to you or do you think I will need more?

I also just wondered about the 12v rails in psu's. Is it better to get a psu with one single dedicated 12v rail or to get one with multiple rails e.g. two or more?

Thanks,
John
 

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VoG

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you don't need a 750W or 850W psu for the your spec, thats massive overkill. 600W to 650W would be more than ample unless you have plans to CF/SLI at a later date.
 
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I think you could power it off a Corsair CX430W. Components don't draw anywhere near as much as they used to.

My Phenom II @ 3.8 and HD6870 (a high end card) with 2 HDDs and 1 optical drive only draws around 320W from the wall under load.

However, might be nice to get a 650W, just so you have ability to SLI in future.

So, either of these would be a good bet:

- Corsair TX650W

- XFX 650W XXX Modular

Or, if you don't care about modular:

- XFX Pro 650W Core Edition

And if you don't think you'll ever use SLI, then this will be more than adequate - even for a heavily overclocked 2500k:

- BeQuiet Pure Power L7
 
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Take a look at the Antec Power Supply Calculator.

650W will be plenty for that spec. Buy a decent branded psu like Cookeh has listed don't buy a cheap and nasty one, they don't last and when they fail they can fry your mobo etc.

I've had a PSU fail on me but luckily everything was ok.
 
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you don't need a 750W or 850W psu for the your spec, thats massive overkill. 600W to 650W would be more than ample unless you have plans to CF/SLI at a later date.

Is there a drawback to having an overspec PSU? I was aiming for a ~500W PSU in a new SB rig, but may SLI/CF at a later date, so thought 650-700W would be better. (I'd rather spend £20 extra now, rather than £70 on another PSU if I upgrade).

The question is : assuming a ~300W power draw, is there any difference between a 500W and 1000W PSU? (Assuming they are equally efficient)
 
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The question is : assuming a ~300W power draw, is there any difference between a 500W and 1000W PSU? (Assuming they are equally efficient)

in terms of power draw you answered your own question there mate, with the bit in brackets :p

a higher wattage unit may get warmer/noisier, as it has bigger capacitors and other hardware inside.

most power supplies are at their most efficient when at 50-75% load, and specific efficiency curves can be easily found if you search around

for example here's one for my PSU
hx850efficiencychart.gif


anything with an 80plus certificate gold or silver will be pretty negligible difference in power draw

@OP: as mike and others said just get a decent branded, 650w unit and you will be fine even if you decide to multi-gpu at a later date

edit: as for the question about rails in the OP, the experts still debate this issue to this day, too many rails and it makes it easier to overload one with a powerful graphics card, but this is more of a concern for lower power units

basically for shopping purposes, ensure that one rail alone can power your graphics card (a flagship type card (with 2x6pin or 6+8pin power) draws no more than 25A)
 
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