I'm having the same issue. Game seems to play fine for a bit, but then I start hearing the sound crackling and popping, and frame rates drop. Checked performance monitor in task manager and all 4 CPU cores pegged out at over 90%. CPU and GPU temps at 63 C. Using Mantle API at ultra settings 2560 x 1440 resolution. Low settings and/or DX11 makes no difference to the problem. Runing latest Catalyst drivers and game is patched. Not having issues with any other graphically intensive games such as Tomb Raider or Thief on ultra.
Windows 7 Pro SP1 64-bit
Intel i5 4690k
16 GB DDR3 @ 2400
Sapphire Radeon R9 290 Tri-X OC
500 GB Crucial M550 SSD
really sounds like you guys are using the onboard gpus instead of your actual graphics card. that's the only time i had issues like you all are mentioning was when my Thinkpad kept switching to it's Intel 4000 gpu instead of my graphics card.
game is running awesome, except for random DirectX Device Error crashes, on my OC'd FX8350 & OC'd 4GB GTX770.
