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GPU Power Delivery

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|DFA| Havoc

Limp Gawd
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Joined
Aug 4, 2014
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205
Alright, so I just picked up a couple of Dell Optiplex 790s with i5 2400 CPUs and Q65 motherboards, and I'd like to move them over to new cases with new power supplies and then add some discrete video cards. However, in classic Dell fashion, the proprietary motherboard design seems to only supply 35W to the PCI-E slot instead of the standard 75W.

My question then is this: How do video cards with auxiliary power connectors decide where to pull their juice from?

If it's a card that draws 100W for example, does it draw 75W from the PCI-E and 25W from the aux? Does it pull from the aux first? Or does it just pull from wherever power is available? I'm guessing it's the last option, but I don't know enough about electrical theory or video card design to know for sure.

Anyone able to shed some light on this for me?
 
all cards will draw all the needed power from the PCI-E power connectors, IF the card ins't able to receive all the power requested from the PCI-E power connectors then it will start to draw from the PCI-E Rail... so if a card require 100W to work, it will draw all of those 100W from the PCI-E power connectors always as possible..

in fact IIRC the PCI-E 3.0 standard force the manufacturers to design the boards to use the 100% of the power from the PCI-E power connectors instead of the PCI-E rail always as possible..
 
I would be inclined to guess it pulls an equal load from each cable if i understand your question. This would make the most sense in my mind since you wouldn't want one cable at max load and then one pulling hardly nothing...good question though
 
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