Date: Sun, 30 May 2021 12:52:16 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=256261 Bug ID: 256261 Summary: TSC-low hardware timer breaks C-States on Intel Core2 generation of CPUs Product: Base System Version: 13.0-STABLE Hardware: amd64 OS: Any Status: New Severity: Affects Many People Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: firstname.lastname@example.org FreeBSD users with an Intel Core2 CPU have reported broken C-states for a while now, as originally reported here: https://forums.freebsd.org/threads/c-states-not-used.66192/ The CPU would refuse to enter any C-state higher than C1. As a result power consumption suffered. Luckily this is a known issue in DragonFlyBSD, with hardware timers being at fault ( https://www.dragonflybsd.org/docs/user/Powersave/#index1h2 ). The fix for FreeBSD is simpler: Simply changing the hardware time to anything other than TSC-low fixes the issue and the CPU enters C2 and higher. Eg. kern.timecounter.hardware=HPET A quick workaround would be to disable the TSC-low timer on all Intel Core2 CPUs, by lowering it's timecounter.choise score. -- You are receiving this mail because: You are the assignee for the bug.