Yep, I've seen youtube videos with them, they are similar to IDE cords, you just plug the one end in the PCI slot and the other to the gpu. granted you have to do a little ghetto riging to get all of them going, but that's the process. Altho the guy at the computer store I goto said trying to run 4 GPU's on 1 PS is impossible, 3 max, but that would work for me.
The 7970's only use 1 of the slots, but they are so thick that it blocks the other available port. I could possibly remove the cover off the card but that voids the warranty, and if these burn out then I'm stuck.
It should also be noted that when connecting more than 3 GPUs on a MB, you need "powered" risers, soerboard. that your GPUs grab their BUS power from the PSU instead of from the moth. Otherwise you could end up frying your MB or GPU.