From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.genesippc.com (mithrandir.softwarenexus.net [66.98.186.96]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 850A767A60 for ; Fri, 23 Jun 2006 20:43:51 +1000 (EST) Received: from p54b0d8f3.dip.t-dialin.net ([84.176.216.243] helo=yukito) by mail.genesippc.com with esmtpa (Exim 4.62 (FreeBSD)) (envelope-from ) id 1Ftj4v-000KDw-Dp for linuxppc-dev@ozlabs.org; Fri, 23 Jun 2006 10:39:58 +0000 From: "Matt Sealey" To: Subject: cpu power "management" for non-dfs chips with no pmu (for instance, 750cxe and mpc7447 in pegasos) Date: Fri, 23 Jun 2006 05:43:43 -0500 Message-ID: <018201c696b1$e942ba40$99dfdfdf@bakuhatsu.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Reply-To: matt@genesi-usa.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Is there any support for using the ICTC to reduce CPU power and so on for PowerPC currently, in absense of a real PMU like on Macs, or the dual-PLL/DFS/DFS4 stuff in newer G3 and G4 chips? I was wondering if there were any definitive performance benchmarks to see if the setting had any appreciable effect in the first place. If it doesn't do much more than kill a couple of milliwatts and the switch between ICTC settings has too high a latency, it would make no sense in a desktop system. I am basically trying to evaluate if we can do ANYTHING to reduce power consumption of systems which are idle, as I have noticed that for running firmware (sitting at a Forth prompt) and booting a Linux kernel and doing some work (for instance a simple benchmark), power consumption barely changes at all. The difference between an idle G4 and a running G4 is negligible. RC5 makes a big difference but it is heavily tuned. Most people won't run RC5 all the time to stress the CPU to the level that it wants to draw a couple extra watts, I think. Comments? :) -- Matt Sealey Manager, Genesi, Developer Relations