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Question regarding powering GPU

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a c 130 U Graphics card
July 22, 2009 8:12:21 AM

Hi,

I have a board that has a 24 pin connector and on it there is a socket to plug in the adapter that usually comes with the GPU, (Molex to PCIE). The idea is that when running Crossfire its used to power the second card.

So the question is would you use this connector or would you use a PCIE from the PSU first ? Also my PSU has a single PCIE connector so could i in theory power a card like a 4870 that needs 2 connectors, I'm assuming the connector on the Motherboard doesn't come from the same +12v rail as the PCIE cable or do you think it would.


Mactronix

More about : question powering gpu

a b U Graphics card
July 22, 2009 12:23:42 PM

"I have a board that has a 24 pin connector and on it there is a socket to plug in the adapter that usually comes with the GPU, (Molex to PCIE). The idea is that when running Crossfire its used to power the second card. "

If I understand your question, the answer is no. The 24 pin connector is the main power connector. The molex connector on the motherboard is there to provide supplementary power to the motherboard. It is not intended to provide power to a GPU.

Let's say that you have a PSU with a single PCI-e power connector and you have a video card that needs two power connectors. You use the single PCI-e connector on the video card. You use the molex to PCI-e adapter to convert PSU molex connectors for use with the second graphic power plug.

If your PSU is of adequate capacity, do not worry about which 12 volt rails provide what power. If your PSU is inadequate, it will not work.
a c 130 U Graphics card
July 22, 2009 12:35:23 PM

Ah i see, I was told that the extra 4 pins on the 24 pin supply as opposed to the 20 was for providing extra power to PCIE slots, this had me wondering what the connector was about but it makes more sense the way you are explaining it. So if i want to run Crossfire i just plug in a spare HDD plug. ;) 
Seems odd that the board would need extra juice to run in Crossfire though or is this common ?
Thanks for the help, it didnt seem right to me which is why i asked

Mactronix :) 
!