Date: Wed, 28 Jul 1999 13:46:32 -0700 From: Mike Smith <mike@smith.net.au> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/i386/apm apm.c apm_setup.s apm_setup.h src/sys/i386/isa clock.c Message-ID: <199907282046.NAA00544@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 28 Jul 1999 22:32:16 %2B0200." <65418.933193936@critter.freebsd.dk>
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> In message <199907282022.NAA25414@freefall.freebsd.org>, Mike Smith writes: > > > In reality, even this isn't good enough; regardless of whether we support > > APM or not, the system may well futz with the CPU's clock speed and throw > > the TSC off. We need to stop using it for timekeeping except under > > controlled circumstances. > > I'd rather we stop using if it looks manipulated. I have looked at various > ways to improve the calibration of the TSC by spending longer time doing it, > this is however not enough to detect a manipulated TSC because the timeouts > in the bios may be half and whole hours. Basically, the BIOS' behaviour has to be considered to be nondeterministic. > It can probably be detected by examining "elapsed wall-clock time" in > hardclock, and comparing to hz with some margin for jitter. Go for it... -- \\ The mind's the standard \\ Mike Smith \\ of the man. \\ msmith@freebsd.org \\ -- Joseph Merrick \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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