This thread is really starting to turn into a flame war, but the specifications that you posted were for an 8-pin EPS power cable, not an 8-pin PCIe power cable. It says right on the website “Make sure that you don’t try to plug an 8 pin 12 volt cable into the 8 Pin PCI Express power connector on a video card. The two cables look very similar so it’s easy to get the two confused.”
Great, I have confused the cables. Though I do not understand the (150 W)=225W. How do you compute?
Great - 225W I got it.
No there was not a war just a flame which we solved with physics. :-) Also it is very pedadodical for other people (including me) to know what is going on with the PSU and its supply to the GPU so 300W is the limit. Fully grasped why.
Also you said for each 6-pin and 8-pin so you meant total. Let me restore this also because I was about to loose my hair since I thought that you meant that current passed from all lines. :-)
So concluding because it is interesting verifying the numbers with the card-specs
The Motherboards through the PCI-epxress can supply 12V with 12.5A current = 75W
The PCI-e 6-pin cable can supply 12V through three lines at 2.083A = 75W
The PCI-e 8-pin cable can supply 12V through three lines at 4.167A = 150W
So for example the Nvidia GTX-275 consumes 219W at its highest load thus there is a need for 2 6pins
The GTX-480 consumes 250W so there is a need for a 6-pin and an 8-pin PCI-e in your PSU board.
Nice info if you plan to go SLI you need this info to calculate the PSU you need.