From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262283AbVAUGnz (ORCPT ); Fri, 21 Jan 2005 01:43:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262285AbVAUGnz (ORCPT ); Fri, 21 Jan 2005 01:43:55 -0500 Received: from smtp-105-friday.noc.nerim.net ([62.4.17.105]:55307 "EHLO mallaury.noc.nerim.net") by vger.kernel.org with ESMTP id S262283AbVAUGnm (ORCPT ); Fri, 21 Jan 2005 01:43:42 -0500 Date: Fri, 21 Jan 2005 07:46:24 +0100 From: Jean Delvare To: Nicolas Pitre Cc: LM Sensors , lkml , Jonas Munsin , Simone Piunno , Greg KH Subject: Re: 2.6.10-mm2: it87 sensor driver stops CPU fan Message-Id: <20050121074624.3db5af6a.khali@linux-fr.org> In-Reply-To: References: Reply-To: LM Sensors , LKML X-Mailer: Sylpheed version 1.0.0 (GTK+ 1.2.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Nicolas, > I confirm that 0x7f is full speed. So at least the polarity bit is correct, and Gigabyte isn't to blame. > > Once you know if the polarity is correct, you can try different > > values of PWM between 0x00 and 0x7F and see how exactly your fan > > reacts to them. > > That's where things get really really interesting. As mentioned > above 0x7f drives the fan full speed (2596 RPM). Now lowering that > value slows the CPU fan gradually down to a certain point. With a > value of 0x3f the fan turns at 1041 RPM. But below 0x3f the fan > starts speeding up again to reach a peak of 2280 RPM with a value > of 0x31, then it slows down again toward 0 RPM as the register > value is decreased down to 0. > > Bit 3 of register 0x14, when set, only modifies the curve so the > first minimum is instead reached at 0x30 then the peak occurs at 0x1d > before dropping to 0. > > Changing the PWM base clock select has no effect. Wow! Unexpected, to say the least. First time I see such a behavior. Could it be that your CPU fan isn't a simple passive device but one of these high-tech models with an embedded thermal sensor and automatic speed adjustment? This would possibly interact with the motherboard PWM capability and could explain the strange speed curve your obtained. I would also like you to try a similar test with your case fan. Enable "smart guardian" mode for this one (by writing 0x73 to register 0x13), then scan the 0x7f-0x00 range (register 0x16) like you did for your CPU fan. I wonder if you will obtain the same kind of result or a standard linear curve. (Note that PWM2 might not be wired at all on your motherboard, so don't be surprised if the case fan speed doesn't change at all.) Thanks, -- Jean Delvare http://khali.linux-fr.org/