Resolved Do I need +3.3V on PSU

I believe that I may have a power supply issue on my hands.
This is a related question to my other Post that has been practically resolved.
This issue has arisen since I connected my OCZ 500W PSU to the Gigabyte
GA-MA790X-UD4P Motherboard. The machine powered up perfectly and booted into Windows. I turned off the PC once or twice then it would not boot up anymore with continuous short beeps that the board manual relates to: Power error. When I connect my PSU Tester all LED's light up exept the +3.3 V.
What makes me now very suspicious is the fact that this PSU was in a different PC that also stopped booting, with no beeps in that case and I had suspected a dead motherboard, but now I am not so sure about this any more.
So if anyone can tell me what effect a non existing 3.3V would have I would appreciate that.

 

I think one should ignore this post for the time being, as a retest with the PSU tester has come up OK now the +3.3V seemed to have been a not properly inserted SATA connector.
Re-seating all power connectors have also given the PC a single Post beep again.
Sorry for jumping the Gun.
hawk22

 

Should this problem arise again, you definitely need the +3.3V. Note that 3.3 / 2 = 1.65V - a very common voltage used by the motherboard to power RAM, the CPU, and other critical components. Also critical are +5V and +12V.