From owner-freebsd-current Sun Feb 11 08:31:36 1996 Return-Path: owner-current Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id IAA13941 for current-outgoing; Sun, 11 Feb 1996 08:31:36 -0800 (PST) Received: from tfs.com (tfs.com [140.145.250.1]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id IAA13936 for ; Sun, 11 Feb 1996 08:31:31 -0800 (PST) Received: from critter.tfs.com by tfs.com (smail3.1.28.1) with SMTP id m0tlegT-0003wuC; Sun, 11 Feb 96 08:31 PST Received: from localhost.tfs.com (localhost.tfs.com [127.0.0.1]) by critter.tfs.com (8.6.12/8.6.12) with SMTP id RAA06667; Sun, 11 Feb 1996 17:25:59 +0100 X-Authentication-Warning: critter.tfs.com: Host localhost.tfs.com didn't use HELO protocol To: Bruce Evans cc: current@freebsd.org Subject: Re: calibrating clocks In-reply-to: Your message of "Mon, 12 Feb 1996 01:43:56 +1100." <199602111443.BAA13304@godzilla.zeta.org.au> Date: Sun, 11 Feb 1996 17:25:58 +0100 Message-ID: <6665.824055958@critter.tfs.com> From: Poul-Henning Kamp Sender: owner-current@freebsd.org Precedence: bulk > >You know about the counter in the APIC too ? > > >It runs at the "bus frequency" but that may vary as well :-( > > No. What's an APIC? I found the description of the counter, pretty damn useless for our purposes I presume, since the bus-clock can be tweaked for power-mgt. There is support for one-shot and periodic mode. IRQ on zero count. It runs of the bus-clock (60/66MHz) there is a prescaler taking 1,2,4,8, 16,32,64 or 128. The counter itself is 32bit, and it's memory-mapped. There is a R/W Initial count register and a R/O Current count register. If IC is 'N' then the CC runs N, N-1, N-2 ... 2, 1, N, N-1 in periodic mode. CC is loaded from IC when you write to IC. There is also an erratum that says that they got it wrong the first time around, nothing major, just the zero-tick being being the width of the input (bus ?) clock rather than zero. -- Poul-Henning Kamp | phk@FreeBSD.ORG FreeBSD Core-team. http://www.freebsd.org/~phk | phk@login.dknet.dk Private mailbox. whois: [PHK] | phk@ref.tfs.com TRW Financial Systems, Inc . Future will arrive by its own means, progress not so.