I am currently trying to build my pc, and when i came to wireing the 5970's i don't know what to do with the 8 pin thingy, it didin't come with the graphfic card nor the powersupply. I looked on youtube of how to install a 5970 and etc, and they just had 1 long cable with the 8 pin thingy which goes from the psu to the gfx, i only got the 8 pin thingy and then it splits into 2 wires with a 3 pin thingy in each end, i am completly lost here. Please help!
With the 5970, you should be using one 8-pin connector (the one you've already identified) for the first connection.
For the second, you should be using a PCI-Express 6 Pin connector- if you have the correct power supply, these PCI-Express 6 pins should come with a separate 2 pin connection on the same cord- making it effectly an 8-pin connector.