Igor from Igor’s Lab has gotten his hands on one of the ROM files for the Navi 21XT (RX 5800XT) graphics card, giving us an idea about the boost clocks achievable on these GPUs. Using the MorePowerTool, he was able to determine that the maximum possible boost clock on Navi 21 will be a whopping 2.8GHz. However, you won’t be able to achieve these figures using normal methods. You’ll most certainly need liquid nitrogen for the GPU core and perhaps, even then the in-game clocks will settle for around 2.5-2.6GHz.
Keep in mind that this is a third-party AIB card and not the reference model from AMD, and will likely come with liquid cooling. The stock GPU limit is 255W, with the maximum being 293. Adding the memory and board power, you get approximately 315-320W of TBP, the same as the RTX 3080.
Now, as far as the stock clocks are concerned, this (possibly liquid-cooled) has a boost clock of 2.57GHz. This is, however, the maximum boost clock and not the average in-game clocks which should be around 2.35-2.45GHz, depending upon the load and thermal solution used. 95 degrees is still the throttle point for the GPU hotspot temp which means north of this, the clocks will start dropping and the performance will slightly degrade.
Once again, this brings us to the same conclusion. The performance on Big Navi will vary significantly from OEM to OEM. Liquid-cooled models might as well be up to 15-20% faster than the reference model, depending on how well the latter runs.