ATI HD 3850 AGP the usual power supply question

So, found some very conflicting answers on the topic.

Bought the card, ATI Radeon HD 3850 AGP. Plugged in, didn't work. Even the fan didn't start. Tried uplugging the extra 6pin power supply, the fan started, but still got no picture.

The card asks for 450W 12V 30A. My old PSU was only 300W, so I went and bought a new one. Trust 520W Pro. Connected everything, and it still don't work, with precisely the same effects.

What could be wrong? I have an onld ATX2.1 motherboard with 20 pins instead of 24 for main power supply. Could this be the problem. I checked my local PC supplier, and he said none of ATX2.2 compliant motherboards have AGP slots, but rather PCIe.
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  1. Welcome to the forums!

    Do you have a Dell, HP or something like that?

    Can't find any honest specs on the Trust 520W. How many amps are on the 12v rails? Look at the label on the power supply.

    Certified power supplies are recommended. Refer to for a list of Certified products.
  2. Says 12A 144W on one 12V rail, and 16A 192W on another one. I have my brother's built-up computer, so I'm not sure about the true specifications. :(
    Can the 20pin motherboard power supply be the problem?
  3. PS: the last VGA card was a low-end nVidia 6600 FX.
  4. In addition, can someone explain me how to read these charts correctly? Say: - shows 18A on all rails. Does it mean it won't work anyways? According to the official site, it does. :S
  5. The 20 pin does not matter.
    You really can't add up 12+16=28, it's more like you have 23 amps on the 12v rails, which could be your problem. You say you need 30 amps on the 12v rails.
    On the OCZ you have 48.33 amps on the 12v rails. 580/12=48.33
    The OCZ would be fine for your card.
  6. Thanks, that explains much. It seems my new PSU still not powerful enough to run it.

    But how would you explain, that without the extra 6pin power cord attached, at least, the fan starts spinning, while with everything connected and all - it just won't start?

    I've read many forums that claim that "it might be running unstable" or whatever, due to low power. While mine just doesn't work at all.
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