Power Supply Recommendations

What power supply should I buy?

I planned to build a PC as follows -

ASUS P8P67 mobo
Internal CPU cooler (heat pipes and two fans)
Quad Core CPU 2600K
XFi Audio card and Internal audio "drive"

Two ATI Radeon HD6870 cards in Crossfire mode

128 GB SSD (OS and apps, only)

1TB external USB HDD (for mass storage)

I'm concerned my existing 650 W power supply may be too small. What symptoms would I see if the PS was underpowered?
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  1. Two 6870s can be done on a 650W unit. What 650W do you currently have in there?

    If your PSU was under powered you might get erratic behavior or your system shutting down when under heavy load.
  2. If your power supply unit doesn't have at least a +12 Volt continuous current rating of 35 Amps or greater then it's under powered.

    Look for a power supply that has at least four PCI Express Supplementary Power Connectors. This is easier to find on 750 Watt and greater power supplies.

    The following reputable name brand power supply units have four PCI Express Supplementary Power Connectors :

    Antec TruePower New Series 650W (TP-650)
    +12 Volt continuous current rating of 54 Amps

    Corsair Enthusiast Series TX750 V2 (CMPSU-750TXV2)
    +12 Volt continuous current rating of 62 Amps

    Corsair Enthusiast Series TX750 Semi-Modular (CMPSU-750TXM) Coming soon
    +12 Volt continuous current rating of 62 Amps

    Corsair Professional Series HX650 (CMPSU-650HX) Semi-Modular
    +12 Volt continuous current rating of 52 Amps

    XFX Core Edition 650W (P1-650S-NLB9)
    +12 Volt continuous current rating of 53 Amps
  3. My mistake, the supply is rated at only 600W not 650 W. It is a CoolerMaster RS-600-ASAA. It has 38 A total for the 12V bus listed as the "Continuity (A). Let's assume they meant "Continuous (A)". The 38A comprises three sections - 16A, 14A and 8A.

    Maybe the problem is I have overloaded the 12V section I am using. Perhaps I should feed each card from a different 12V section (via two different harnesses) rather than both from one harness (which I did to simplify the wiring).
  4. First, 38 amps from a 600 watt PSU is pitiful. A good 550 watt PSU should produce at least 40 amps.

    Second, most PSU's advertised as "multi-rail" really aren't.
    Single vs. multiple rails:
  5. http://www.coolermaster.com/product.php?product_id=39

    The link above takes you to the product description on the CoolerMaster web site. I believe it is a decent power supply and is not "pitiful". You just have to be careful not to compare peak output ratings with continuous ouput ratings. Peak output of the supply is 58A on the 12V bus.

    So, I had this power supply sitting on my workbench and installed it last night. This beast can source 98A on the 12V bus. It runs very quietly, which I love. I still have both cards on the same 12V bus (dumb!). I'll rectify that tonight.


    Here's a funny thing I just found. CoolerMaster recommends putting only one PCI-e card on each 12V cable BUT they provide two PCI-e connectors on each cable. <-- this is a "mistake" waiting to happen.
  6. forget coolermaster, unless you buy their really high end psu's, they are poor performers. they are not great value for money either way.
  7. I did not intend to use that PSU for this PC but it is installed and I think I will just leave it there. It is waay over-powered but as a consequence, it runs cool and quiet.

    Thanks for the help. I guess I will look for Antec and Corsair next time.
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