Intel Processor Diagnostic Tool Test: Ran without any errors
Hot CPU Tester 4 Pro: Ran without any errors
Prime95 (Blend + Small FTTs): Ran without any errors
Memtest86: Ran without any errors
Process Explorer: Seemed to eliminate any theories about 'memory leaks'
GPU-Z Render tests report that both cards are running at x8 3.0 so at first thought, there doesn't seem to be anything wrong with the motherboard.
My PSU seems to be fine; I haven't received any random crashes when playing games at full load, running benchmarks, or stress testing.
As I've mentioned before, I've tried a few different drivers, I've tried each card on their own in the primary slot and they perform completely fine.
Firestrike Graphics Score (1GPU): 10422
http://www.3dmark.com/3dm/3790152
Firestrike Graphics Score (2GPUs): 20118
http://www.3dmark.com/3dm/3790193
Furmark average 1GPU: 62FPS
Furmark average 2GPUs: 124FPS
My Firestrike Graphics Score seem absolutely fine for 2GPUs; fullinfusion received a score of 20035 with 2x R9 290 like myself -> The scores are similar so based solely on that, there's no need for worry about the GPU.
During Furmark, if the temperatures are fine, then both GPUs are steady at around 100% usage:
As soon as GPU1 hits 94 degrees, it throttles back and yet it still tries to push to 100% usage. However, when GPU1 throttles back, even though GPU2s stats haven't decreased(core+memory), the usage fluctuates... 37%,65%,72%,50% etc.....................................(To 'Random Murderer', ULPS is not disabled)
Although, realistically, from all the games I have played, GPU1 hasn't gone above 80-85, and GPU2 hasn't gone above 70-75 so this throttling issue shouldn't affect the FPS I get in games.
FPS With 1GPU (Highest settings unless otherwise stated):
Battlefield3: 85-100
Battlefield4: 80-95 (MANTLE)
Crysis3: 85-110 (No AA)
NeedForSpeedTheRun: 60-90
F1 2013: 95-130
FPS With 2GPUs
Exactly the same... (The games are played at full screen)
I honestly have no idea what is wrong....
The benchmarks and tests conclude that there is nothing wrong (as far as I'm aware) with my computer, so it doesn't make sense as to why I wouldn't gain any advantage using the second card.