From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 26 Aug 2001 19:01:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 26 Aug 2001 19:01:06 -0400 Received: from smtp-ham-2.netsurf.de ([194.195.64.98]:52410 "EHLO smtp-ham-2.netsurf.de") by vger.kernel.org with ESMTP id ; Sun, 26 Aug 2001 19:00:53 -0400 Date: Mon, 27 Aug 2001 00:40:07 +0200 To: Alan Cox , Dieter =?iso-8859-1?Q?N=FCtzel?= , Linux Kernel List Subject: Re: VCool - cool your Athlon/Duron during idle Message-ID: <20010827004006.A10483@storm.local> Mail-Followup-To: Alan Cox , Dieter =?iso-8859-1?Q?N=FCtzel?= , Linux Kernel List In-Reply-To: <20010826181315Z271401-760+6195@vger.kernel.org> <20010826220023.G2994@cerebro.laendle> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20010826220023.G2994@cerebro.laendle> User-Agent: Mutt/1.3.20i From: Andreas Bombe Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Aug 26, 2001 at 10:00:23PM +0200, Marc A. Lehmann wrote: > On Sun, Aug 26, 2001 at 08:24:20PM +0100, Alan Cox wrote: > > Well my German isnt that good, > > the page is in english (at least the one you get while clicking on > linux, which is german and english alike, and gthe source code is rather > international ;) > > > but it appears to be just another variant > > on CPU idling. > > The linux version only fiddles with a single bit in the northbridge that > is claimed to be necessary so the cpu goes into the "real" idle mode. It > also warns that some streaming applications might react to this with frame > drops or similar. According to c't 18/2001 p.36, the real power saving in halt and STPCLK is only in effect when the CPU disconnects from the FSB. In the VIA north bridges there is one bit (bit 7 at offset 0x52) which controls whether the north bridge performs the disconnect protocol. For various reasons, this is usually disabled by the BIOS: 1. Lower quality power supplies and motherboard voltage regulators may not be able to deal with the large and fast current changes. 2. Disconnect costs 2% - 3% on common benchmarks. Incidentally, this is also the difference between the fastest and slowest Athlon motherboards. Disconnect doesn't sell, benchmarks do. 3. The internal clock generator of the CPU may lose sync or something on reconnect. (erratum #11, can be worked around by software) 4. In rare cases, Athlons with non-integer frequency multipliers (e.g. 7.5) may fail to reconnect altogether. (erratum #14, work around: don't sleep in C1 or C2 with disconnect) Errata as quoted from the article, referring to "AMD Athlon Processor Model 4 Revision Guide", http://www.amd.com/products/cpg/athlon/techdocs/pdf/23614.pdf -- Andreas E. Bombe DSA key 0x04880A44