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PCIe Power Questions

L

llee

Golden Member
1. I understand that a motherboard's PCIe x16 slot is able to supply 75w 12v DC to any dedicated graphics card that is connected. Did the PCIe 3.0 standard change any of these figures?

2. Do dedicated graphics cards that have PCIe 6-pin and 8-pin power connectors draw power simultaneously from the PCIe slot and 6/8-pin connectors or is it a measure to ensure backward compatibility with older boards power wise?

3. If you have multiple graphics cards using the PCIe slot to draw power does each card draw power independently from each other or is it divided equally from a larger pool dedicated to the PCIe bus?
 
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Pretty sure #2 is yes, they use both PCI-E power as well as the 6- and 8-pin PCI-E power connectors.

As far as #3, some boards (IMHO, better-designed ones) have a molex power connector on the board, near the PCI-E slots, to provide extra 12V power to the PCI-E slots.

My MSI K9A2 Platinum board is like that. It has FOUR PCI-E slots (2.0 x8 each one).
 
#2 is yes. Dedicated GPUs often draw more total power than the cables can supply. E.g. 7850 draws more than 6-pin can supply, 560 Ti draws more than 2x6-pin, and GTX580 draws more than 6+8pin
 
Thank you. It appears that PCIe 1.0, 2.0, and 3.0 x16 slots are all able to provide up to 75w of power to add-on cards.
 
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