so just finished building a new tower, hooked up my GPU (radeon HD6870) from my old pc with the same PSU (OCZ600MXSP) so it boots up fine when when all i have a is the mobo (ASRock 990FX Extreme) and GPU hooked up but when i plug in a black power cable from PSU to CPU connecter i got nothing, even if i remove the end connected to the CPU i still get nothing, any ideas?