Date: Tue, 12 Nov 2002 14:57:37 -0500 (EST) From: John Baldwin <jhb@FreeBSD.org> To: "Dr. Michael Mackey" <mackey@engineering.uiowa.edu> Cc: freebsd-alpha@FreeBSD.org Subject: Re: Extreme time drift in SMP mode Message-ID: <XFMail.20021112145737.jhb@FreeBSD.org> In-Reply-To: <3DD12AA2.8D84B3E2@engineering.uiowa.edu>
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On 12-Nov-2002 Dr. Michael Mackey wrote: > You're right, the clock on the Lynx (2100a) is an 8254: > > (from the output of dmesg) > FreeBSD 5.0-CURRENT #0: Mon Nov 11 15:31:50 CST 2002 > mackey@home.:/usr/src/sys/alpha/compile/HOME > Preloaded elf kernel "/boot/kernel/kernel" at 0xfffffc00006c2000. > DEC AlphaServer 2100A > AlphaServer 2100A 5/300, 291MHz > 8192 byte page size, 2 processors. > CPU: EV5 (21164) major=5 minor=5 > OSF PAL rev: 0x4000100020116 > real memory = 199155712 (189 MB) > avail memory = 187490304 (178 MB) > FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs > --- snip --- > Timecounters tick every 0.976 msec > Timecounter "i8254" frequency 1193182 Hz > --- snip --- Hmm, what does it look like with a UP kernel? It would be using the "alpha" timecounter right? Also, how often do timecounters tick with the UP kernel? It's usually every 10 msec on all the systems I have that are running current. > John Baldwin wrote: >> >> On 11-Nov-2002 Andrew Gallatin wrote: >> > >> > Michael A. Mackey writes: >> > > It takes precisely twice as long (20 seconds) to run `sleep 10`. >> > > >> > > Why can't ntpd keep things in line? >> > > >> > >> > Because its not desgined to fix a clock which is that broken -- it >> > only increments a second or so at a time. Far too slow for your >> > purposes. >> >> So the clock is running at half-speed now? Hmm, the 2100[A] are >> Tincup, not Turbolaser, right? So it should be using the i8254 for >> its timecounter. Maybe the 8254 timecounter isn't setup right on >> the 2100a? >> >> -- >> >> John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ >> "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ > > -- > Prof. Michael A. Mackey (michael-mackey@uiowa.edu) > Biomedical Engineering / Radiology > University of Iowa, Iowa City, Iowa > Voice: 319-335-6058 Fax: 319-335-5631 > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-alpha" in the body of the message -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-alpha" in the body of the message
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