Clock running fast

[Anthony Atkielski]

Ted Mittelstaedt writes:

> Anthony, you really need to look in the code sometime:

It takes a very long time to find relevant sections of code, and unless
the author was very conscientious, there are usually few or no
explanatory comments, anyway.

> /usr/src/sys/dev/acpica/acpi_timer.c

Thanks.

> * If all tests of the counter succeed, use the ACPI-fast method.  If
> * at least one failed, default to using the safe routine, which reads
> * the timer multiple times to get a consistent value before returning.

Whatever that means.

> /usr/src/sys/i386/isa/clock.c
> /usr/src/sys/i386/i386/tsc.c

Thanks

> /*
> * We can not use the TSC if we support APM. Precise timekeeping
> * on an APM'ed machine is at best a fools pursuit, since
> * any and all of the time spent in various SMM code can't
> * be reliably accounted for.  Reading the RTC is your only
> * source of reliable time info.  The i8254 looses too of course
> * but we need to have some kind of time...
> * We don't know at this point whether APM is going to be used
> * or not, nor when it might be activated.  Play it safe.
> */

Hmm.  I think APM is turned off on my machine, at least that's what
FreeBSD says.  The manual for the MB doesn't say anything about SMI use.
I don't like the idea of a motherboard stealing cycles from my machine;
it sounds way too much like a virus, and a virus built into the hardware
is the worst nightmare.

-- 
Anthony