I recently switched from an Intel i7-7700k (@ 4.8 GHz) on an Asus Maximus IX Formula to an AMD Ryzen 3900X @ stock speed on an Asus Crosshair VIII Formula.
I carried over the RAM (G.Skill 3600 CL16), the GPU (AMD Vega 64 LC) and the rest of the stuff (Samsung NVMe, etc.). So I basicly just swapped mobo and CPU.
I was actually not expecting a huge bump in FPS, since my old CPU wasn't the bottleneck here. But the new 3900X shouldn't struggle either with "keeping my Vega busy". But when benchmarking (3D Mark, Ghost Recon Wildlands, RB6 Siege, AC Odyssey) I am constantly getting 5-6% less FPS (compared to the 7700k) now. Needless to say that I am a little dissappointed by that. How is that happening?
Already checked if the GPU runs at x16 bus speed and yes it does.
Temps are fine also, got a custom loop that keeps the CPU around 55°C on max load.
Also checked RAM/IF speed and they are 1:1.
Here is my 3D Mark result comparison: