Date: Wed, 28 Jul 1999 22:32:16 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Mike Smith <msmith@FreeBSD.org> 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: <65418.933193936@critter.freebsd.dk> In-Reply-To: Your message of "Wed, 28 Jul 1999 13:22:31 PDT." <199907282022.NAA25414@freefall.freebsd.org>
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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. It can probably be detected by examining "elapsed wall-clock time" in hardclock, and comparing to hz with some margin for jitter. > Curse the lack of a dependable high-resolution timer. Curse the focus on windows in hardware design... -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message
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