Message-Id: <200305112048.h4BKmdkc006140@turing-police.cc.vt.edu>
To: Andrew McGregor <andrew@indranet.co.nz>
Cc: Tuncer M zayamut Ayaz <tuncer.ayaz@gmx.de>, linux-kernel@vger.kernel.org
Subject: Re: 2.5.69 strange high tone on DELL Inspiron 8100 
In-Reply-To: Your message of "Sun, 11 May 2003 23:28:25 +1200."
             <3191078.1052695705@[192.168.1.249]> 
From: Valdis.Kletnieks@vt.edu
References: <1405.1052575075@www9.gmx.net>
            <3191078.1052695705@[192.168.1.249]>
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On Sun, 11 May 2003 23:28:25 +1200, Andrew McGregor <andrew@indranet.co.nz>  said:

> cpufreq and speedstep don't work on Dell P3 laptops anyway, and the 
> *internal power supplies* of the i8x00 series make wierd noises when APM 
> tries to idle the CPU.  The board will do this anyway, without making 
> noise, so linux need not.

Dell Latitude C840 (1.6G Pentium4 Mobile) has the "power supplies buzz at 1Khz
on APM idle" symptom too. I haven't checked the ACPI side of the fence yet, nor
have I gotten brave enough to try the cpufreq and speedstep stuff.

Even *more* bizarre, there's "something odd" done by the seti@home client
(which usually causes 100% CPU use and thus silence) several minutes into a
workunit that causes  the noise to change frequencies - it will start down
around 500hz, sweep up to 1Khz (taking about 2 seconds to do so), and repeat
(so the buzzing is exhibiting a sawtooth wave).  I'm not seeing any paging
or swapping or I/O, so I'm wondering if it's some code walking through a large
array with strides 1/2/4/8/16 (like an FFT) causing different cache hit ratios,
and thus different power consumption patterns while it's stuck on a L1/L2
cache miss.....


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