Date: Mon, 20 Sep 1999 09:06:26 -0700 From: Doug <Doug@gorean.org> To: David Schwartz <davids@webmaster.com> Cc: Mike Smith <mike@smith.net.au>, Poul-Henning Kamp <phk@critter.freebsd.dk>, hackers@FreeBSD.ORG Subject: TSC vs. I8254 (Was: RE: cvs commit: src/sys/i386/conf files.i386 src/sys/i386/i386 mp_clock.c) Message-ID: <37E65B82.D60552D8@gorean.org> References: <000001bf0347$bd39b3e0$021d85d1@youwant.to>
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> > > No, the TSC is far superior on UP, (unless destroyed by APM), it > > > has roughly 100 times better resolution and is twice as fast to > > > query. If y'all don't mind, I have a slightly related question. I have a 5 year old Dell computer that started life as a P90, which I overclocked to run as a P100 by moving the bus speed up to 33 from 30 for a long time without apparent problems. Then about 2 years ago I got one of those fancy OverDrive chips (a 150, which was what was rated for my board, which I overclocked at the same bus speed to run as a 166). After a few months of running fine about every other boot up freebsd would report the wrong clock speed. It was always a seemingly random value, with no pattern I could discern. On a tip from one of the lists I started experimenting with the CLK_ options in LINT, and finally found one in the 2.2.x branch that managed to get me the right clock speed on say 9 out of 10 boots, so I was happy. That option (options "CLK_USE_I586_CALIBRATION") went away in 3.x, so now I'm down to choosing between options "CLK_USE_I8254_CALIBRATION" and options CLK_USE_TSC_CALIBRATION. I tried the I8254 option first, and it gives me what I want, namely the right cpu speed on every boot. However based on the conversation regarding this thread I'm wondering if I should try the TSC calibration method instead? I know that someone will be tempted to warn me about the evils of overclocking, but please don't. :) However, just in case anyone is interested either the overclocking or the overdrive chip seems to have fried the on-board serial ports on this machine. I've been trying for months to get a serial console on it, and couldn't figure out why all I ever got was garbage no matter how many different configurations I tried. Well, I'm finally in a position where I have a third computer to try, and lo and behold my workstation machine can run a serial console just fine, but the server machine was all scrambled. So, last night I bought a serial port card and voila, FINALLY I have a serial console. TIA for any insights, Doug To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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