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Wattage and Total Amp requirement for HD 5770

I am building a system with an HD 5770 graphics card, and I was prepared to order a 600W power supply...until I started reading into choosing the 12V rails. I am confused.

Assuming I am buying a power supply with a single rail...does the total amps at which a Power supply run always correlate to the total wattage? For example, will a 600W power supply always have about 40 amps in its 12v rail and will a 750W power supply always have about 50 amps in its 12V rail?

How many watts and how many amps on the 12V rails should my power supply have if I am getting an HD 5770 card?

Thanks.
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  1. Best answer
    Nope, wattage ratings on the sides of the PSUs dont mean a thing.

    This diabletek unit is a great example of how little rated wattage means, go to the pictures and find the image of the sticker, you will see its only rated for 530W on the 12V rail, or about 44A, but its also listed as a 750W unit.
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817822010

    Now if you look at the antec TP-550, you will see it has 45A on its 12V rail, its rated 200W lower, but provides an extra 12W where it matters.
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817371020&Tpk=TP-550

    There is a lot of variation in quality between PSU manufacturers and between models in a manufacturers lineup unfortunately. When shopping for PSUs always look for the max load table, on newegg its usually one of the images. If its not skip that PSU and move on.

    As a general rule of thumb a good 500-550W unit with ~40A on the 12V rail will run any single GPU card, a good 700-750W unit with ~60A on the 12V rail will run most crossfire or SLI setups. The 5770 is low power so you could safely crossfire it on a quality 650W unit.
  2. http://www.amd.com/us/products/desktop/graphics/ati-radeon-hd-5000/hd-5770/Pages/ati-radeon-hd-5770-system-requirements.aspx

    450 Watt or greater power supply with one 75W 6-pin PCI Express® power connectors recommended (600 Watt and two 6-pin connectors for ATI CrossFireX™ technology in dual mode)

    The amp requirement fir the 5770 is often overstated.

    If you aren't overclocking, then the above will work.....if doing serious OC's, the sweet spot will be 650 watts for a single GPU setup and 850 for twin GFX cards....the latter also leaves room for a dedicated PhysX card. The reason I says weet spot is that quite often a PSU of 500 watts will be almost the same price as the 650 watter. For example:

    500 watts $69 http://www.newegg.com/Product/Product.aspx?Item=N82E16817371007
    650 watts $79 http://www.newegg.com/Product/Product.aspx?Item=N82E16817371015

    For comparison purposes , the list below contains performance ratings (10 scale) at jonnyguru.com / prices as per newegg on 02/21/2010 and ones w/ double asterisks (**) made it onto silentpcreview.com's Editor's Choice List meaning they excelled at both electronic and acoustic performance:

    850 watters

    Antec SG-850 - 10.0 ($220) **
    Antec CP-850 - 10.0 ($110) ** (requires compatible case)
    XFX 850W Black Edition 10.0 ($185)
    Corsair HX850 850W - 10.0 ($180)

    Antec TruePower Quattro (TPQ-850) - 9.5 ($150)
    Corsair TX850 - 9.5 ($140)
    Seasonic M12D 850W - 9.5 (NLA) **
    NorthQ Giant Connector 850W - 9.5 (NFS)
    Etasis ET850 - 9.5 (NLA)
    Silverstone Zeus ST85ZF - 9.5 (NLA)

    Enermax Revolution 85+ 850W - 9.0 ($250)

    Thrmaltake Toughpower XT 850W - 8.5 ($216)
    OCZ Z Series 850W - 8.5 ($200)

    NorthQ Black Magic Flex 850W - 8.0 (NFS)
    Coolmax CTG-850 - 8.0 (NFS)

    SilverStone Decathlon DA850 - 7.5 ($230)
    Enermax Galaxy DXX 850W EGX850EWL - 7.5 (NFS)

    SilverStone Strider ST85F - 7.0

    Silverstone Element ST85EF 850W - 6.0


    650 watters

    Antec Signature 650W (10.0) OOS **
    Seasonic X-650 650W (10.0) $160 **
    Silverstone Olympia OP650 (10.0) NFS

    Thermaltake Toughpower QFan 650W (9.5) NLA

    Antec Earthwatts EA650 650W (9.0) $75

    Antec True Power Trio 650W (7.5) NLA

    XFX XPS 650W XXX Edition Power Supply (7.0) NFS

    Antec NeoPower Blue 650W (6.5) NLA

    BFG BFGR650PSU 650W (6.0) NLA

    NorthQ Black Magic Flex 650W PSU (5.0) NFS

    NFS - Not For Sale / NLA = No Longer Available / OOS - Out of Stock
  3. Best answer selected by booleanyesno.
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