This probably isn't it, but it might be worth checking. I saw that your friend had 1 stick of ram and you have 2, and at a higher clock. You should be getting 'better' cpu performance off of dual channel, if it is indeed running in dual channel (which it might not if they aren't in the right slots). Or your Mobo mightn't've loaded any, or an incorrect xmp profile and thus only running at 1333. Anyways, if the system RAM is screwy in any way it could be causing some intermittent cpu bottlenecking. Its always good to eliminate a possibility regardless.
Also a longshot, could your bios be setting your pcie link speed at something less than gen2 8x? I'm not sure if thats even possible....but that could explain why the less powerful 760 performs closer to expected and the 290x doesn't. Presumably though, if the 290x cant throughput all its data it wouldnt be working as hard and wouldn't be getting that hot (much like putting vsync on in an older game barely stresses gpu)
Best of luck!
looking at your mobos specs your board only supports pci-e 2.0 that said supposedly newer amd drivers can compress the data sent to the gpu so it shouldn't be that much of a problem. also make sure you have your card in pci-e slot 1 the website has a note about it suggesting something may go wrong if you use other slots it outside of crossfire.
Okay I'm 99% sure it's my GPU now.
I just reformatted again to 8.1, and installed latest GPU drivers. I then went into Unigine Valley with no MSAA and only at high this time (I usually turn everything up). OC'd I was getting around 3200 when I am supposed to be getting to 4400. I did the Set CPU affinity thing and limited to 4 cores and my score stayed the exact same.
But are you watching for thermal throttling? That is a big problem with the new AMD cards. Especially if you are overclocking. Watch the clock speed and see what happens to it.
Highest I have seen them go is 53C on the first and 70C on the second.
If I turn powertuner off the core clock will go to 900MHz until the fan ramps up then it goes back to 1000MHz.
When I am "OC'ing" I set the fan a lot higher and it will stay in the 80-85C range and the core will not leave 1000MHz for a second.
Yeah, sounds like the gpu is messed up. Contact the manufacturer or the seller. See if you can get a replacement.