Date: Thu, 5 May 2005 12:53:38 -0700 From: "Ted Mittelstaedt" <tedm@toybox.placo.com> To: <freebsd-questions@freebsd.org> Subject: RE: Clock running fast Message-ID: <LOBBIFDAGNMAMLGJJCKNOEEPFBAA.tedm@toybox.placo.com> In-Reply-To: <995071073.20050505131333@wanadoo.fr>
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> -----Original Message----- > From: owner-freebsd-questions@freebsd.org > [mailto:owner-freebsd-questions@freebsd.org]On Behalf Of Anthony > Atkielski > Sent: Thursday, May 05, 2005 4:14 AM > To: freebsd-questions@freebsd.org > Subject: Re: Clock running fast > > > 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. > find /usr/src/sys -print |grep "whateveryourlookingfor" can help. > > /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. > TSC, dummy, or i8254, probably depending on the results of other tests. > > /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. > It is probably a tossup between the i8254 driver taking cycles to run and an internal kernel counter based off the CPU clock taking cycles to run. Ted > -- > Anthony > > > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "freebsd-questions-unsubscribe@freebsd.org" >
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