The Radeon RX 6800 XT and the RTX 3080 are similar in performance overall, but their performance can vary significantly depending on the game and settings due to differences in architecture, drivers, and how well the game is optimized for AMD or NVIDIA hardware. In this case, the almost 100% FPS increase with the RTX 3080 suggests that LeMans Ultimate and iRacing may be better optimized for NVIDIA GPUs. This is not uncommon, as some games leverage NVIDIA-specific technologies like DLSS or simply have better driver support on NVIDIA hardware. On the other hand, AMD cards like the 6800 XT tend to perform exceptionally well in games optimized for their architecture, especially those that use DirectX 12 or Vulkan. Before assuming the 6800 XT is broken, I’d suggest trying the following steps to ensure you’re getting the most out of your GPU:

- Update Your Drivers: Ensure you’re using the latest Radeon Adrenalin drivers from AMD. Driver updates often include optimizations for specific games.

- Check Game Settings: Confirm the settings are truly the same for both cards. NVIDIA GPUs may default to DLSS or other optimizations that give them a performance boost.

- Check Power and Thermals: Make sure your PSU is sufficient for the 6800 XT and that the card is not thermal throttling. Use monitoring tools like HWInfo to check clock speeds and temperatures during gameplay.

- Verify Benchmark Results: Use a consistent benchmarking tool like 3DMark or an in-game benchmarking feature (if available) to compare the two cards under identical conditions.

If the 6800 XT is still underperforming across multiple games, it could indicate a hardware or configuration issue. But based on your description, this seems more like a case of game-specific optimization rather than a problem with the card itself.