How Does the GTX 460 Use More Power Than The PCI-E Connectors Allow?

sgtmattbaker

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Aug 21, 2009
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Right here: http://www.tomshardware.com/reviews/geforce-gtx-460-gf104-fermi,2684-13.html

The GTX 460 at load uses 250 watts of power. Ok, well, the Geforce GTX 460 has 2 PCI-E 6 pin connectors and the PCI-E slot. Each PCI-E connector can deliver up to 75 watts (while the 8 pin connectors can deliver up to 150) and the PCI-E slot in the motherboard can deliver up to 75 watts. So, 75*3 = 225 watts. How does the card use more watts than its connectors allow? If one of the connectors was an 8 pin connector there wouldn't be any confusion at all.

I know that the PCI-E connectors have their own dedicated 12V rails (or either a couple connectors share a 12V, but no other devices like hard drives or anything get power from that same rail), but I was under the impression the 6 pin connector just did not supply more than 75 watts.
 
Thats the system power consumption at the wall, so there is the efficiency of the PSU to factor in there too which means that the system as a whole was actually pulling less than what is stated there by about 15% as far as the output side of teh PSU was concerned.


Its actually uncommon for PCI-E connectors not to share with anything, usually the CPU will get one, and the PCI-E connectors will get paired with some SATA and molex connectors to spread the load across a few.

Now technically there is nothing saying that a 6 pin couldnt provide the 150W you get from an 8 pin with no problem, the two extra pins are just additional grounds so the 4 12V lines are already plenty strong to provide the full 150W, its just a design technique, but technically you could design a GTX 580 with only a single 6 pin PCI-E connector and it would likely be able to handle the power draw without issue, but its frowned upon as having multiple connectors makes it clear for the user if their PSU is going to be strong enough or not.