Hi, I have slightly different problem with slightly different HW (FX APU, same GPU) so this may be unrelated but try this kernel: https://uloz.to/!qq2wDEC87/linux45-4-5rc6-1-x86-64-pkg-tar-xz (it's from Manjaro, works just fine in Arch). If I wait 2 minutes before booting the system I have no problems as long as I don't suspend it. It may be more stable for you too.