Do I need a 750w or 850w psu?

[yusux]

I want to build a new comp soon, heres what I have in mind

i7 920
x58 mobo
6gb ram
2x ati or nVidia
2 sata HD
physx card
dvdburner

I will be ocin' the i7 and the video cards, I could use some advice on which PSU to get since theres so many on the market.

 

[HOOfan 1]

2x ATI or nVidia what? Knowing what card matters.

If you want 2x HD4870X2 or GTX295...then you will want to lean towards a quality 850W.
If you want 2x GTX 285 and major ocing 800W+

Anything lower than that should be ok with a quality 750W.


What do you want to spend?
If you want quality and value...Corsair TX850.

If you want pinnacle of performance Antec Signature 850, Seasonic M12D 850W or Enermax Revolution 85+ (runs from 850W-1050W)

 

[yusux]

What's the difference between a PFC psu and a non-pfc psu?

 

[HOOfan 1]

A PSU with PFC has power factor correction non-PFC doesn't

Read the sticky at the top for more info but basically with the way a PSU uses AC power, the wave form put back into the mains is different than that going into the PSU. With DC power, since there is no waveform and the current is always flowing in a single direction, current * Electrical potential (volts) always equals Power (watts). Since the current flow reverses back and forth in AC power and since the PSU both stores power and has elements that resist the flow of electrons back into the mains, the actual power it is using in watts is different than the apparent power that it is using (VoltAmps=Volts*amps).

Power factor=Real power (watts)/apparent power(VoltAmps). A power factor of 1 is perfect.

Any high quality 750W+ unit is going to have active PFC, meaning that you won't see that red voltage selection switch.

 

[yusux]

are power effiency really that important, it only seems to save 1~10 dollars a year

 

[HOOfan 1]

Originally posted by: yusux
are power effiency really that important, it only seems to save 1~10 dollars a year

Low efficiency costs you more in heat than it does in money. Most electricity that is not put to work in your PC but is being pulled from the wall outlet, is going to be lost as heat.

Most quality units today will be fairly efficient.

 

[faxon]

Originally posted by: HOOfan 1

Originally posted by: yusux
are power effiency really that important, it only seems to save 1~10 dollars a year

Low efficiency costs you more in heat than it does in money. Most electricity that is not put to work in your PC but is being pulled from the wall outlet, is going to be lost as heat.

Most quality units today will be fairly efficient.

dont forget that as a result, the PSU wont last as long due to hotter operational conditions it has to work under. not good for the longevity of the device for sure