On Tue, Apr 29, 2014 at 11:36 AM, ron minnich <rminnich@gmail.com> wrote:

Anybody out there know typical numbers for the timer tick if USB is
active as part of SMM?

I just heard one number for one product line, 8 HZ. We're seeing a
mysterious 18 HZ tick on one system. Any other numbers people know?

18.2 Hz is legacy stuff, http://wiki.osdev.org/Programmable_Interval_Timer - but the particulars of an SMM implementation might just as well be a copy-paste error, for all I know.

An OHCI driver might use a timer tick to recover after a timeout. The USB spec doesn't specify all the timeouts, though multiples of 100ms are common (so a ~10HZ timer might be useful).

Hope that helps,
David