Since I have changed to Windows 10, I started having constant problems.
My 7970 is now almost constantly stuck at 500/150 MHz - this seems to happen, when I turn on Opera browser, or MSI Afterburner, but clocks don't change even after turning both off, I always have to restart the computer. Card was undervolted and underclocked for most of the time lately - 800 MHz at stable voltage, done via MSI Afterburner. I have not touched Wattman/Overdrive for graphics.
This did not really happen when I was on Win 7. GPU was stuck at 500/150 MHz on idle, but immediately changed to normal clocks when gaming.
FX 8320, 3,5 GHz.
Asrock FX 990 Extreme IV
Asus Radeon 7970.
2x4GB 1600 MHz Geil.
128GB SSD Toshiba (system and drivers)1TB HDD Western Digital.
Radeon drivers 17.4.4.
Both GPU and CPU have proper cooling solutions, so this is not a problem here.