From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261479AbUCIG6u (ORCPT ); Tue, 9 Mar 2004 01:58:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261500AbUCIG6u (ORCPT ); Tue, 9 Mar 2004 01:58:50 -0500 Received: from fmr99.intel.com ([192.55.52.32]:10953 "EHLO hermes-pilot.fm.intel.com") by vger.kernel.org with ESMTP id S261479AbUCIG6s (ORCPT ); Tue, 9 Mar 2004 01:58:48 -0500 Subject: Re: fsb of older cpu From: Len Brown To: Bjoern Schmidt Cc: linux-kernel@vger.kernel.org In-Reply-To: References: Content-Type: text/plain Organization: Message-Id: <1078815523.2342.535.camel@dhcppc4> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.3 Date: 09 Mar 2004 01:58:43 -0500 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org C-states should be called Idle-states -- they're entered when the processor is idle. No instructions are executed when in a C-state > 0. C1 is supported by all processors automatically with some carefully placed insructions inside the idle loop. Not all processors suport higher C-states with more power savings in idle. You'll be able to tell what is supported and what is used by looking in /proc/acpi/CPU0/power. I'm not sure we update the counter to reflect entering C1... Then there are P-states -- performance states. These are used by the various cpufreq drivers such as speed-step(tm;-). These can modulate both voltage and Mhz at the same time depending on load and are thus the most effective and most desireable way to save cpu power w/ minimal performance impact. Thermal throttling is something else. This is invoked as the passive-colling method of last resort when the processor is very hot (busy). The actual clock to the processor is modulated so that it slows down and thus power is saved in proportion to how much it is slowed down. Throttling will noticeably slow down your system when you want it fast the most -- heavy load. Of course, then there is active cooling -- fan control... cheers, -Len On Mon, 2004-03-08 at 16:53, Bjoern Schmidt wrote: > Stefan Smietanowski schrieb: > > I'm no expert on the subject but as I recall the processor sets the > > internal clock (derived from fsb+multiplier) on startup so no matter > > what you do do the running cpu it won't change it. > > I think there must be a way. In the BIOS there ist an option "half > processor > clock it is in idle". One time i have seen in /proc/cpuinfo" that the > clock > was at ~118MHz, but that is 6 Month ago and i have this never seen > again... > The problem is that with activated acpi the passive cooling does not > seem to > work although the cpu is very often in C2 and throttling mode is at 8. > C1 is > called extrem rarely (~1000 times per day), even if the system is > under heavy > load for a long time. I believe that C2 is not really supported by the > cpu. > > -- > Greetings > Bjoern Schmidt > > > - > To unsubscribe from this list: send the line "unsubscribe > linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >