A loop buffer in a CPU’s frontend stores previously fetched instructions, allowing small loops to be contained for power savings and potential performance boosts. The loop buffer feature, used by Intel, Arm, and AMD cores, is present in Arm’s Cortex A15 and Zen 4 AMD processor. Zen 4’s loop buffer behaviors and effects on performance with BIOS updates have been detailed through experimentation and SPEC CPU2017 scores. Surprisingly, Cyberpunk 2077’s performance shows a slight decrease with the loop buffer disabled on certain die configurations. AMD’s decision to disable the Zen 4 loop buffer was likely due to cautious validation processes rather than notable performance impact.
https://chipsandcheese.com/p/amd-disables-zen-4s-loop-buffer