(In reply to Alex Deucher from comment #63)
> 
> Are you forcing the power state to high?  The mclk shouldn't be affected by
> the display clock.

No, setting the refresh rate to 144 results in high mclk, even when I set
power_dpm_force_performance_level to low or pp_dpm_mclk to 0. Using 120 Hz, I
could echo 0 or 1 to pp_dpm_mclk. I also got the power meter on now:

memory dpm state 0  (150 MHz):  77 watts
memory dpm state 1 (1250 MHz): 112 watts

So there is a difference of 35 watts. Using Windows, I'm below the 80 Watts
even with 144 Hz.