Overclocking

Overclocking the RX 6900 XT is similar to the RX 6800 XT in that you must increase the power limit. By default, the card runs into its power limit all the time, which constrains the clocks—any additional overclock will not yield higher frequencies. Once you've dialed up the power limit, overclocking works very well.

AMD has raised the overclocking limit for the maximum GPU frequency to 3000 MHz, which sure is nice, but highly unlikely to be achieved. My card topped out at 2810 MHz boost, so there is plenty of headroom; maybe they should have raised the memory limit instead, or just removed those limits completely.

I also figured out how to get 100 MHz higher memory clock. By default, the "VRAM Tuning" section gives you a slider that's percentage based, going up to 107%. Maxing that out will clock memory at 2140 MHz (2000 MHz * 1.07). When you switch to "Advanced Control," you get a slider that's MHz based and goes up to 2150 MHz, or 107.5%.

What's REALLY surprising here is that the ASUS STRIX 6800 XT at maximum OC is significantly faster than the AMD RX 6900 XT at maximum OC. It looks as though the AMD power limit is still too low after the manual increase, so the card can't clock as high as the ASUS card, which has a higher power limit.

Overclocked Performance

Using these clock frequencies, we ran a quick test of Unigine Heaven to evaluate the gains from overclocking.


Actual 3D performance gained from overclocking is 3.7%.