Hello everybody,
since 2 days I have the problem mentioned above. The effective clock (HWInfo) stays at around 100-150MHz for the first core (Core 0), first thread (Thread 0). If SMT is enabled, the second thread's working normally, only the first thread has the problem. The same if SMT disabled: the first thread has a really low effective clock. Ryzen Master shows not the same value, but also a clock which is too low.
To my system: Ryzen 3800XT, X570 Phantom Gaming 4 (BIOS 3.40), 4x 8GB Ripjaws V (DDR4-3200).
Temperature could be a problem. Prime95 on both threads of the first core shows the same result, effective clock is pretty low. Prime95, 2 workers only on the first thread increases the temps about 5°C (in relation to the test on both threads).
If more details are needed, I can provide more.
Kind regards
Le Duc Lischetzke