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Thread: HD 4870 x2 on 500W ?

  1. #11
    Join Date
    Nov 2009

    Default Re: HD 4870 x2 on 500W ?

    It would probably work, but why risk it?

    Clean power is always crucial to a solid system.
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    Last edited by mxwritingnow; 11-18-2009 at 06:26 AM.

  2. #12
    Join Date
    Aug 2009

    Default Re: HD 4870 x2 on 500W ?

    Ok guys you convinced me, I'll buy a 750W PSU

    Thanks for help ! :)

  3. #13
    Join Date
    Apr 2004

    Default Re: HD 4870 x2 on 500W ?

    Quote Originally Posted by marko94 View Post
    I saw at Legit Reviews - Technology News and Reviews that Palit radeon hd 4870 x2 even overclocked pulls only 411W so why 750W and not 650W ?
    Because basically watts don't matter but the AMPs the 12v rail/s do.

    Best to get yourself a 750w or better PSU that only has 1 very beefy 12v rail or multi rails that can supply at least 25AMPs on each rail (the sooner these "virtual rail" PSU's are gone the happier I'll be).

  4. #14
    Join Date
    Apr 2009
    J'Habite En Angleterre

    Default Re: HD 4870 x2 on 500W ?

    As long as the PSU has a single 12V rail and isn't in a virtual rail config then judging using wattage of the 12V rail is perfectly valid. The important figure is Combined Amperage or Wattage on the 12V rail(s) noting that on multi rail units adding up the capabilities of each rail may come to more than the combined figure states is allowed.

    It's just Ohms Law. a PSU with a single rail capable of supplying 700W max to the 12V rail will always have the same Amperage (58 1/3A, just as a PSU with a single 12V rail and a 58.3A capability will have the same Wattage capacity (700W).

    It gets confusing when you move to virtual rails. A PSU may be capable of supplying 50A combined on all the 12V rails, and also have the rails rated something like 25A, 30A, 20A. This doesn't mean the manufacturer is being dishonest or is lieing to you, it means that thek know in some cases not all rails will be loaded equally and they allow you to be able to draw more on an individual rail for flexability, as long as combined you don't go over the combined total.

    This config is not to be confused with some units that have two 12V rails set up like for example the Corsair HX1000. The HX1000 is two 520W PSU's joined into one unit and thus has two independent rails, both capable of outputting half the total Wattage/Amperage.

    Virtual rails aren't inherantly evil, they are just in some cases harder/more confusing to set up correctly so that you've spread the load of the PC equally over all rails available.
    Coolermaster CM 690 II advance Case
    Corsair HX750 (CWT, 91%(80+ Gold rated @230V) single 62A 12V rail
    P55A-UD4 v2.0 @ F14
    Core i5 760 @ 20 x 201, 4.02GHz
    TRUE Black with a single Noctua NF-P12 pumping out 55 CFM @ 19db .
    2 x 2GB Mushkin Ridgeback (996902), @ 7-10-8-27, 2010-DDR, 1.66v
    2 x Gigabyte GTX 460 1024MB in SLI (Pre OC'd to 715MHz core and 1800MHz VRAM) @ 850 Core / 4100 Mem.
    Intel X25-M Boot Drive (OS and Programs) 200MB/s Read & 90MB/s Write
    Corsair X32 200MB/s Read & 100MB/s Write
    WD Caviar Blue 640GB C (Steam, Games, Storage, Temp Files & Folders, etc)
    Samsung F3 500GB Backup/Images
    Noctua 1300RPM 19dB case fan (rear extraction)
    3 x 140 MM Coolermaster LED fans (one front intake, one top extraction, one side intake)
    Dell Ultra Sharp 2209WAf E-IPS @ 1680x1050

  5. #15
    Join Date
    Dec 2006
    San Francisco, CA

    Default Re: HD 4870 x2 on 500W ?

    My GTX 295 runs fine on my Ultra 650watt that I bought 2 years ago for $60 bucks..

    But seems like buying a solid power supply would be a wise decision.
    Case: Antec P180 ** PSU: Ultra-V 600W
    Main: EVGA 680i 122-CK-NF68**
    CPU: E6700 2.66GHz
    CPU cooling: Arctic Freezer 7 Pro ** RAM: 2GB Corsair XMS2
    GPU: BFG GTX 295..** Samsung 206bw LCD
    OS: Vista Ultimate 32bit

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