On Maw, 2005-11-08 at 04:53 -0800, Zachary Amsden wrote: > Can't hurt, and APM is largely obsolete because of ACPI, so I'm only > concerned with trimming and keeping adequate protection of the kernel > from APM code while maintaining correctness. I don't have a nice set of > old machines with enough wacky APM BIOSen to validate that unpinning the > CPU is ok. A large number of SMP machines, probably the majority of APM based ones require that APM calls occur on CPU#0. As I understand it from a BIOS engineer involved in debugging that problem Redmond always does APM from CPU #0 and may even guarantee it. Alan