The Guilty Party

So as it turns out my PSU was starving GPU #2 and the CPU for amps when GPU #2 went into 3D mode. Why is this?

It all has to do with how the PSU is laid out electrically (needless to say this was something I should have paid more attention too when buying the PSU, but it was on sale at newegg.com and I didn't do as much research as I should have. What can I say?)

So here is how this OCZ GameXStream is laid out:

12v Rail 1: CPU #1
12v Rail 2: PCIe#2/CPU#2
12v Rail 3: Mobo / Acc.
12v Rail 4: PCI3#1

So, whats to wrong with that. Well, what they call CPU#2 is actually the second 4 pin cpu power plug. So if you have a motherboard with an 8 pin cpu power plug you will be using cpu 1 and cpu 2 on this power supply, which I was.

But wait, you say: each rail is rated for 18 amps. That should still be enough right?

Well yes and no. Each rail on it's own could hold an 18 amp load, but if you read the fine print on the PSU label you will see another power restriction. All of the 12v rails combined should never exceed 50 amps and there we reach the real problem.

OCZ reaches a 700 watt output by adding:
155 watts for the +3.3v and +5v rails
525 watts for the +12v rails
20 watts for -12v and +5Vsb

155 + 525 + 20 = 700 watts.

Ok I see that but there are still some things that don't add up. To reach 50 amps on the +12V rails you would need to be pushing 600 watts on the +12V rails, not 525. Oops, that must be some fuzzy math.

Ok so how many amps are you really getting if not 50amps?

525W / 12V = 43.75 amps

Oh boy! So how many of those did we need again?

CPU: 95 watts @ 12V = 7.9 amps
GPU #1: 146 watts @ 12v = 12.2 amps
GPU #2: 146 watts @ 12v = 12.2 amps

That leaves just 11.45 amps or 137.4 watts for the rest of the system, the motherboard, ram, DVD, hard drives, everything.

This math did not work out in my favor. The long story short is that I got an 1100 watt Tagan BZ psu and all the problems went away.

I would have never been able to overclock the cpu with the 700 watt PSU.