Re: 2.5.69 strange high tone on DELL Inspiron 8100

[Troels Walsted Hansen]

Andrew McGregor wrote:
> Try this (which will make no difference to the effectiveness of APM on 
> this machine):
> 
>> CONFIG_PM=y
>>
>> CONFIG_APM=y
>> CONFIG_APM_DO_ENABLE=n
>> CONFIG_APM_CPU_IDLE=n
>> CONFIG_APM_DISPLAY_BLANK=y
>> CONFIG_APM_REAL_MODE_POWER_OFF=y
>>
>> CONFIG_CPU_FREQ=n
>> CONFIG_CPU_FREQ_TABLE=n
>>
>> CONFIG_X86_SPEEDSTEP=n
> 
> 
> Reasoning:
> 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.

My Dell Latitude C600 shows the exact same problem. I noticed it after 
upgrading to from RH7.x to RH8 with kernel 2.4.18-27.8.0. I believe this 
kernel is customized by RH to use HZ=500 or something in that region.

With your analysis of the problem I was able to remove the noise by 
using the "apm=idle-threshold=100" parameter on the kernel commandline. 
This turns off APM idle calls without requiring kernel recompilation.

Using the "i8k" kernel module, I have verified that the temperature of 
the CPU is unchanged with APM idle turned off. I have not tried to 
measure power consumption or battery use.

Thanks for the tip!

-- 
Troels Walsted Hansen