From owner-freebsd-acpi@FreeBSD.ORG Wed Apr 28 14:34:39 2004 Return-Path: Delivered-To: freebsd-acpi@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2EB3A16A4CE for ; Wed, 28 Apr 2004 14:34:39 -0700 (PDT) Received: from mail2.speakeasy.net (mail2.speakeasy.net [216.254.0.202]) by mx1.FreeBSD.org (Postfix) with ESMTP id E1A8543D3F for ; Wed, 28 Apr 2004 14:34:38 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Received: (qmail 17934 invoked from network); 28 Apr 2004 21:34:38 -0000 Received: from dsl027-160-063.atl1.dsl.speakeasy.net (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) encrypted SMTP for ; 28 Apr 2004 21:34:38 -0000 Received: from 10.50.40.205 (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.12.11/8.12.11) with ESMTP id i3SLYYvM016922; Wed, 28 Apr 2004 17:34:35 -0400 (EDT) (envelope-from jhb@FreeBSD.org) From: John Baldwin To: freebsd-acpi@FreeBSD.org Date: Wed, 28 Apr 2004 17:34:46 -0400 User-Agent: KMail/1.6 References: <20040428211826.A02195D07@ptavv.es.net> <20040428142302.T89203@root.org> In-Reply-To: <20040428142302.T89203@root.org> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200404281734.46945.jhb@FreeBSD.org> X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on server.baldwin.cx cc: Jeffrey Katcher Subject: Re: Fan Control Success on IBM T40? (another quick Q) X-BeenThere: freebsd-acpi@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: ACPI and power management development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 28 Apr 2004 21:34:39 -0000 On Wednesday 28 April 2004 05:24 pm, Nate Lawson wrote: > On Wed, 28 Apr 2004, Kevin Oberman wrote: > > > Date: Wed, 28 Apr 2004 13:15:13 -0700 (PDT) > > > From: Nate Lawson > > > Sender: owner-freebsd-acpi@freebsd.org > > > > > > I forgot to add -- the reason the clock rate announced at boot time is > > > different is because the test for CPU TSC is done before acpi is > > > enabled. At some point when the SMI is disabled and acpi enabled, the > > > clock rate is switched by your BIOS to the lower rate. You can see > > > this because the clock rate announced by the TSC timecounter will be > > > ~600 mhz while the initial boot clock rate will list ~1600 mhz. > > > > This all makes sense, but it conflicts a bit with my > > observations. (Probably implies something bad about my powers of > > observation.) > > > > I boot and the system (T30) is running at 1.8 GHz. I throttle the CPU. > > Testing clearly shows that the throttling is working. I use the test you > > suggested of calculating an MD5 hash of a big string of zeros. > > > > But, when I "count cycles" to test the CPU speed (code appended), I > > still see 1.8 GHz. > > > > Why don't I see the speed reduced when throttling? I suspect my lack of > > fundamental understanding of the interactions of throttling and the ACPI > > clock. > > This is totally different. You aren't using SpeedStep/performance states, > only throttling. Throttling works by changing the duty cycle but with the > SAME base clock rate. Since the TSC comes from the base rate, your test > reading the TSC will never change. Also, even with SpeedStep, the CPU will "fake" the TSC so that it stays at a constant rate even when the CPU is throttled down to a slower speed. I think that's what the 'ACPI' bit in the cpu_features indicates. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org