(In reply to haro41 from comment #122)
> In my experience, this issue is related to mclk switching and it affects the
> lowest mclk level only.
> 
> So you guy's can save a lot of power, if you, insteed of switching to
> highest gfxlevel or to disable vsync, just disable the lowest mclk level by:
> 
> echo "manual" > /sys/class/drm/card0/device/power_dpm_force_performance_level
> echo "1 2 3" > /sys/class/drm/card0/device/pp_dpm_mclk
> 
> If you are building your kernel locally, look in this thread for a driver
> code modification that works, without disabling the lowest mclk level (saves
> a few watt on idle).

Ooh, that seems to have solved it. Haven't had a crash yet, ran The Outer
Worlds for hours (addicting game!), ran FFXIV, ran GW2, no lockups. And, if
there is much of a difference at idle in watt usage, I don't see it on the UPS
meter.

Thanks a million!

(also of note, when using the valve ACO, as others have noted, you don't even
have to do the above to (apparently) solve the problem. unfortunately, that has
other issues, my V64 wont clock up high enough when using ACO for some reason,
so i dont use it).