I can only assume you considered and rejected this idea for an explanation for the confusing performance drop in Cyberpunk, but just in case... I'd put my money on some difference other than the disabled loop buffer between the different firmware versions.
Intel has apparently disabled the LSD on Skylake (SKL150 erratum) and Kaby Lake (KBL095, KBW095 erratum) chips via a microcode update and on Skylake-X out of the box, due to a bug related to the interaction between hyperthreading and the LSD
I can only assume you considered and rejected this idea for an explanation for the confusing performance drop in Cyberpunk, but just in case... I'd put my money on some difference other than the disabled loop buffer between the different firmware versions.
Intel has apparently disabled the LSD on Skylake (SKL150 erratum) and Kaby Lake (KBL095, KBW095 erratum) chips via a microcode update and on Skylake-X out of the box, due to a bug related to the interaction between hyperthreading and the LSD