While the Radeon RX 6000 series had an artificial clock speed limit set at 3.0GHz, it appears that the limit has been pushed up to 4.0GHz on the latest refresh, the GPU known as the Navi 21 XTXH.
This allowed Der8auer to push Powercolor's newest Radeon RX 6900 XT Liquid Devil Ultimate graphics card to 3,225MHz by dropping the temperature down to about -87C on LN2.
The Powercolor Radeon RX 6900 XT Liquid Devil Ultimate also did well without LN2, where Der8auer managed to get an overclock of +280MHz, up to 2820MHz at 86C in the 3DMark Time Spy benchmark.
AMD has managed to refine the Navi 21 GPU to a level where it does perform a lot better but bear in mind that these are binned chips, and we are not sure how many AMD will manage to push to the market.