Find 12 V 4pin to 8 pin EPS adapter

Check your motherboard manual to make sure you actually need the adapter. Many motherboards will work with just a 4pin power plug. Some motherboards actually come with a little plastic cover on 4 of the 8 pins. That is a pretty good sign the motherboard will work with a 4 pin power cable.

Thank you. I knew that. I found them on Newegg.

Yeah, it worked fine for me on stock settings. But when I gave the processor a little more juice, I had to buy an 8-pin to reach the last couple of hundred MHz.

Save your money. An adapter will not increase the amount of power flowing through a CPU power cable. If your motherboard won't work with a 4 pin cable, it won't work with an 8 pin adapter plugged into the same power cable.

I had the chance to check that out on my Intel board, without the use of the adapter the board will not boot.

power draw usually isn't the issue, it's that the mobo can take advantage of more traces.

I'm trying to figure out why an ATI 5870 has two 6pin PCIe plugs that pull only 75watts each. I either need to get a 6pin Y-cable for both or I need to use two 12v rails because each rail only has 1 6+2pin plug. Each rail can handle ~400watts(33.3amps 40amps max). Why do I need two 75watt 6pin connectors when my PSU can handle 5 times that amount with 1 6pin.

It's not as much a limit of the PSU but a limit of the traces. They need more contacts to distribute the load because those tiny thin trace wires can only handle so much, so they add more pins.

Best answer selected by martinhersey.