[Debian-eeepc-devel] Temporarily disabling lid-close-suspend

Phil Endecott spam_from_debian_eee at chezphil.org
Mon Sep 15 20:05:16 UTC 2008

Damyan Ivanov wrote:
> Leaving your eee unsuspended with the lid closed can be dangerous.  

Well, here are some measurements:

Workload = one thread doing mjpeg decoding and another doing floating 
point maths and sorting, at CPU frequency = 800 MHz or 1600 MHz as 
indicated; or idle.
Ambient temp. = 19 C.
Tk = keyboard temperature, measured with a thermocouple between B, N 
and space.
Tc = CPU temperature as reported by /sys/class/hwmon/hwmon0/temp1_input.
Note that the screen seems to turn itself off when the lid is closed, 
irrespective of what I do in response to the ACPI event.

Lid Open
            Tk    Tc
idle       30    49
800 MHz    30    52
1600 MHz   31    62

Lid closed
            Tk    Tc
idle       37    52
800 MHz    39    57
1600 MHz   40    66

Lid closed, in bag
            Tk    Tc
idle       44    59
800 MHz    48    66
1600 MHz   49    77

Lid closed, tape over fan vents
            Tk    Tc
1600 MHz   49    79

Simply closing the lid increases the CPU temperature by at most 4 C.  
Taking more extreme actions to prevent heat from escaping can raise the 
CPU temperature to 17 C above normal.  The maximum temperature reached 
in these experiments was 11 C below the "critical" threshold set in the 
fan controller (90 C).  You might get closer to the critical 
temperature if your ambient temperature is higher.  I imagine that 
reaching the critical threshold will cause some sort of automatic 
shutdown, but I'm unable to prove that.  My fan seems to have about 3 
speeds, the highest being activated briefly when the temperature 
reached 80 C and immediately bringing it down to 79 C, even with the 
vents jammed up.

The label on the bottom of the Eee shows the numerous safety standards 
that it meets.  It would not be possible for it to get all of these 
certifications if it could catch fire, or even become dangerously hot, 
as a result of this sort of treatment.

Cheers, Phil.

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