Date: Fri, 04 Sep 1998 17:53:00 +0200 From: Poul-Henning Kamp <phk@critter.freebsd.dk> To: Mike Smith <mike@smith.net.au> Cc: Bruce Evans <bde@zeta.org.au>, caj@lfn.org, freebsd-current@FreeBSD.ORG Subject: Re: bzero bandwidth computation Message-ID: <4356.904924380@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 04 Sep 1998 08:44:16 -0000." <199809040844.IAA03514@word.smith.net.au>
next in thread | previous in thread | raw e-mail | index | archive | help
In message <199809040844.IAA03514@word.smith.net.au>, Mike Smith writes: >> In message <199809041132.VAA10135@godzilla.zeta.org.au>, Bruce Evans writes: >> >>>>From a boot -v on my Thinkpad 560E running -current >> >>>(GenuineIntel 166MMX pentium): >> >>> >> >>>i586_bzero() bandwidth = 173130193 bytes/sec >> >>>bzero() bandwidth = 688705234 bytes/sec (!!!) >> >>> >> >>>Hrm, a bit fishy eh? >> >> >> >>APM strikes again I bet... Your CPU clock changed speed while it ran... >> > >> >That might have given a negative bandwidth :-). >> >> No, that would be unlikely. Many APM seem to power up with the CPU in >> a reduced speed mode, and then after a short time the crank it up to >> full speed. > >This usually seems to be about the same time they turn the screen >on. I think this might more likely be a flurry of SMI activity as the >system's warming up the first time around. On some laptops it is up to 10 seconds after jumping to the boot record... >The current set of symptoms *seem* to be related to cycle-counter >related interpolation being off because either the tick rate is erratic >or the CPU speed is non-constant. It's looking like we can't rely on >the cycle counter for accurate timing - this will be an issue with >desktops as PC98 and PC99 systems start to become common too. 8( And people at Intel have said that using the TSC for timekeeping is wrong, and should never have been done, but they decline to provide something better because if NT is so advanced that it can use the i8254, then all we have to do is to improve our OS to the same point :-( -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." "ttyv0" -- What UNIX calls a $20K state-of-the-art, 3D, hi-res color terminal To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4356.904924380>