[MuffloN]

Windows 8.1 x64 fully patched
7850 w/ latest Catalyst (stable, tested latest beta drivers but it did zero difference)
12Gb DDR3-1600
i7 920, 8 [email protected]
Generic Realtek HD soundcard
XBMC 13.2, no addons, no skins, pure vanilla (Tested 14.0 Helix as well, same thing)

Symptom: If I play a video DWM (Desktop Window Manager) goes back to using 0-0.1% of 1 CPU core, if I stop playback or just sit in a menu DWM instantly goes nanners and starts building towards maxing a CPU core, I was even able to play around with it by stopping/starting playback.

All other video players or OpenGL/DX renderers causes no such things, no issues otherwise at all.

Changing rendering method or acceleration does nothing.

Here's a log from when I had 14.0A3 installed

And of course, finally, a log file: https://paste.ee/p/Ml8ta#9JW89oTao9Z8utW...2BoNi3Tq0m

[fritsch]

Catalyst issue - it has problems to do correct vsync - don't use it.

[MuffloN]

Just uninstall Catalyst? Do you mean the driver or CCC? Because it's hard to live without graphics drivers.

EDIT: You might mean disable vsync in CCC, I'll try that and report back.
EDIT2: forcing all vsync off in CCC and rebooting did nothing to curb the problem.

[MuffloN]

Disabling vsync in XBMC only seemed to piss it off even further, the speed which it took to max a CPU core went from somewhat slow to instant 100% usage.

You're on to something, but I don't know what.