What kind of power supply do i need to run 4870 crossfire!

[supernode]

im building a new computer and i need power supply that will power 2 4870, three 500 gig hard drives, phenom II x4 940, 4 gb corrsair memmory and 3 to 5 fans!

I was hoping to keep my cost around $150 maybe a bit more if i really have too!

[Exmortis]

You could get by with a 750w, but if you want some breathing room I recommend the 1000w OCZ EliteXstream. Its well priced, not modular but very cost efective and one slick unit. Reviewed here and on HardOCP.

[SugarJ]

Agreed, a 750 should do it, but an 850 will for sure.

Corsair TX850W 850W CMPSU-850TX 12V 70A 24PIN AT Power Supply Active PFC 140M Fan Powersupply - DirectCanada

$139.

[Oversized Rooster]

I have run dual 4850 cards, 4 hard drives, a quad core Q9450 CPU OCed to 3.8GHz, sound card, lots of fans, etc on a 750W PCP&C Silencer successfully...

[geokilla]

Anything that's a or better than a Corsair HX620.

[rjbarker]

Agreed, a 750 should do it, but an 850 will for sure.

+1

but if you want some breathing room I recommend the 1000w OCZ EliteXstream.

C'mon 1kw is what is recommended for 2 x GTX 280's.....he's got 4870's

[supernode]

thanks for all the answers i was thinking this power supply OCZ ModXStream Pro 700W ATX 20/24PIN SLI Ready Modular Cables 140MM Fan 80PLUS Power Supply or do you think i should go with the 750 watt

[magictorch]

Given the price of the Pc&P or Corsair 750watt PSU's I'd stick with one of those as it will leave some room for other things, plus they are rated at high amps on a single rail. I'm planning on using my Pc&P 750watt to run a 2x4870's and an oc'd i7 with dual watercooling loops, currently have a X3350 right now (no issues). You could always spend a little more if you like on the corsair 850watt.

[stoanee]

From Wikipedia

It's important to match the capacity of a power supply to the power needs of the computer. The energy efficiency of power supplies drops significantly at low loads. Efficiency generally peaks at about 50-75% load. The curve varies from model to model (for examples of how this curve looks see the test reports of energy efficient models found on the 80 PLUS website). As a rule of thumb for standard power supplies it is usually appropriate to buy a supply such that the calculated typical consumption of your computer is about 60% of the rated capacity of the supply provided that the calculated maximum consumption of the computer does not exceed the rated capacity of the supply. Note that advice on overall power supply ratings often given by the manufacturer of single component, typically graphics cards, should be treated with great scepticism. These manufacturers wish to minimise support issues due to under rating the supply and are willing to advise you to overrate it to avoid this.

Also,

There is a popular misconception that a greater power capacity (watt output capacity) is always better. Since supplies are self-certified, a manufacturer's claims may be double or more what is actually provided.[6][7] Although a too-large power supply will have an extra margin of safety as far as not over-loading, a larger unit is often less efficient at lower loads (under 20% of its total capability) and therefore will waste more electricity than a more appropriately sized unit. Additionally, computer power supplies generally do not function properly if they are too lightly loaded. Under no-load conditions they may shut down or malfunction

Here is linky to a calculator;
Thermaltake Power Supply Calculator

[Exmortis]

Nice post Stoanee, especially with regards to under loading a PSU. But in this case, my bet is he will have no such underloading issue. I only recommended the 1k because most people who go CF/SLI tend to always have new and power hungry gadgets to expand their computers, and with the extra breathing room, your covered.

Some nice PSUs suggested, always always though, check the PSU for a HWC, or HardOCP test, I won't buy one that isn't tesed by one of those two, both is even better.