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    Dual 12V PSU Shootout
    Author: JonnyGuru
    Date Posted:21/07/2005 13:42.03
    AMS Mercury PP-44603 SLRating: SLRating: 9/10
    Seasonic S-12-430 SLRating: SLRating: 9/10
    Thermaltake TWV500 SLRating: SLRating: 9/10
    Bottom Line: The three of these power supplies really don\'t shoot-out each other. If you want cheap, the AMS. If you want quiet, the Seasonic. If you want modular, the Thermaltake.

    Find the lowest price for this product - AMS Mercury PP-44603
    Find the lowest price for this product - Seasonic S-12-43
    Find the lowest price for this product - Thermaltake TWV500
    Pages: 1 2 3 4 5 6 7 8
    Discuss This Article


    Introduction

    It's that time again.  I've got three more power supplies with dual 12V rails and a power supply tester waiting to test them.

    I changed some of my loads from the last review.  I didn't blow anything up, so I figured I'd

    Test 1:  .I've got +12V1 and +12V2 at 12A.  I figured this was a good "base" test.

    Test 2:  The +12V1 and +12V2 are juiced up to 14A to emulate a higher than average load.  This may be above spec for some power supplies.

    Test 3:  This test throws the power supply a bit off balance   +12V1 goes up to 16A, while +12V2 goes back down to 12A.  The 5V is brought up to 16A

    Test 4:  This test is the opposite of three.  +12V2 is now at 16A and +12V1 at 12A.  The 5V is still at 16A.

    Test 5:  This test is rather balls to the wall.  The 5V is brought down to 14A, but both 12V rails are whacked with a 16A load.  This is a 32A, or 384W, on the 12V combined rail.  This is out of spec for most power supplies, but I find many can handle this I then move the rails up to a combined wattage of 408W.  This can be done by putting 17A on each rail or 16A and 18A... depending on how the power supply is spec'd.

    The only exception I made for this test is the Seasonic.  Since the Seasonic was only a 430W power supply (I take what I can get) the 12V load was so out of spec the overload protection immediately kicked when I applied it.  For the fifth and final test, the Seasonic gets a 14A load on 12V1, a 15A load on 12V2, a 14A load on the 5V rail and a 10A load on the 3.3V.

    What is a 12V rail and why are there two of them?

    I suppose we should break down what we're talking about here....   The rails (named after steel rails that carried power to electric trains) are what each different colored wire (yellow for +12V, red for +5V, etc.) derive it's power from.  With the demand on +12V becoming greater and greater, Intel decided it would be "safer" to split the duty of supplying +12V across two rails.  It's "safer" because inexpensive transistors capable of supplying more amperage (say more than 34A) at any kind of decent efficiency (70% or better) are subject to blowing up.  :-)  That's not very safe.  ;-)

    To split the duty up between two +12V rails, one can use cooler running, cheaper transistors to supply the power.  Furthermore, this isolates devices on one rail from another, so EMI introduced by lighting inverters and drive motors can be isolated from sensitive components like the CPU and video card.

    (14 * 12) + (16 * 12) = 336?  What is this?  NEW math?

    You'll often find that the capabilities of the +12V rails combined almost never equal what is listed for each rail individually added together.  This is because, although the two +12V rails are on separate transistors, they're still being fed by the same, single transformer and rectifier.  So one rail might be able to pull off 168W if loaded up by itself, and the other might be able to pull off 192W if loaded up by itself, but the amount of juice that can even get to those transistors (safely) isn't more than 336W, so you simply CAN NOT fully load both rails to their maximum capabilities.  And when I say "can not" load them, I mean load them without overloading them and staying within the tolerance of the rated rail.  I mean, I put 16A loads on 14A rails all day long... that doesn't mean it's recommended.  ;)

    So back to the testing!

    So we have our 5 tests, and we also have a +5VSB test that looks at the power factor and efficiency of a power supply when it's idle.  Power factor and efficiency will also be measured under all loads.  All loads are run for 15 minutes prior to deriving a reading and are run for 30 minutes before determining a pass/fail.  The usual stuff.

    Noise will not be measured on a technical level.  As before, I will just give a "judgment" on how loud a power supply is.  If it can drown out my 2 1/2 year old dancing around to the Wiggles in the other room, it's loud.

    Now, on to our testing.... Go the the next page
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    Article Navigation

    1. Introduction
    2. Testing
    3. The AMS Mercury PP-44603
    4. The Seasonic S-12-430
    5. The Thermaltake TWV500
    6. A look at the cables
    7. Load test results
    8. Conclusion


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