motherboard or cpu faulty?

Gigabyte GA 7ZX motherboard with Athlon 900.
I have the board set up on the bench. The cpu fan spins and the green light on the motherboard illuminates. The keyboard flashes once. I have no output to monitor. I have no post beep codes. Even if i remove all drives and memory i still get no beep codes! Other than substitution any sugestions on the most likely component to be failing. The motherboard or the CPU?