how much power supply is ideal for a i5 machine running with 5870 crossfire?
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  1. Head over here:

    And fill out the form.

    Then, you do a little math (result of psucalc * 1.2 = suggested PSU wattage, after efficiency)

  2. A pair of 5870's needs about 300 watts (25 amps) peaking to 400 watts (32 - 34 amps).

    The smallest PSU that I would use is a Corsair 750TX (60 amp 12 volt rail):


    But I'd probably put in an 850.
  3. An 850 should be fine, definitely. I wouldn't use a 750 unless I'm pressed for budgeting.
  4. I don't think I follow JSCs logic at all. I would put both cards at no more then 40A together. If that 750W has 60A total, there is no way the rest of the machine will use the other 20. So why is it bad to use the 750W? Any quality 60A PSU should be fine.
  5. But if I choose to overclock my processor and my graphic cards then?
  6. ATI recommends a 600w PSU for CF 5870s. A high quality 750w PSU will still allow for GPU+CPU overclocking.

    XFX 750 $125

    Seasonic x-750 $153 w/ promo code

    However, if you don't mind paying extra for headroom you might never use (ATI recommends 850w for 2x 5970s, that's 4 GPUs):

    XFX 850 $147

    Corsair 850HX $170

    Antec SG-850 $211
  7. Will you be running one of the 125W+ chips? Even overclocked except for those 125W chips your only looking at 10/11A. Thats still only 50A, and if you can find something to max out both the CPU AND both cards.
  8. Mr.Veteran
    I did not understand your last post. would you please make it easy for me to understand.
  9. What I'm trying to say is even if you are overclocking your CPU, you still won't hit the wall of your PSU. You would have to have one of the most power hungry CPUs (125/130W), overclock it, and then find a way to 100% load the CPU and GPUs to hit the limit of the PSU. Even gaming shouldn't do this.
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