I have this issue for a while and it taken a lot of time to figure it out what's the cause.
After 30 minutes or 1 hour of playing Forza Horizon 4, the game starts to have FPS drop and it's almost unplayable. This was happening all the time. Searching the subreddits, I realized that the issue could be related only to RX 5500 series.
After so many attempts, reinstalling drivers and Windows 10, checking the temperatures and looking for possible hardware issues, I finally managed to solve the FPS drop problem with older driver, with version 19.12.2 to be precise.
I've done some benchmarks comparing 20.4.2 and 19.12.2 drivers. There is big FPS boost and much more stable frame rate with the 19.12.2. I tried the latest optional drivers as well and I got conclusion that from Adrenalin 20.4.2 to 20.7.2 the issue still persist. I didn't tested the game with 20.1.3 and 20.2.2 driver versions.
These are my full PC specs:
Processor: AMD Ryzen 5 2600
Motherboard: Gigabyte AB350M-DS3H V2
RAM: 2 x 8GB DDR4 3000Mhz XPG SPECTRIX D41
Storage 1 (Boot): 120GB Samsung 650 SSD
Storage 2 (Games): 500GB Samsung NVMe 970 EVO
Storage 3 (Misc): 1TB WD Blue
VGA: MSI RX 5500 XT MECH OC 4GB
PSU: Cooler Master G650M
Case: Genesis Irid 300
Monitor: BenQ GW2480 24" IPS
Mouse: Fury Gaming Warrior
Keyboard: Fury Gaming Hurricane TKL RGB
Anyone experiencing the same?
