(In reply to Chernovsky Oleg from comment #29)
> No luck. Tried various hacks and commenting return values.
> 
> Will try mmiotracing these registers from fglrx on weekend

Be careful that to write no irrational values into the PLL registers, e.g.
don't use partly radeon partly fglrx settings.

I once over clocked UVD to 4GHz instead of 400MHz by accident and the card is
still working, but at least in theory you can damage the hardware with that.