[ltp] [PATCH] ibm_acpi - Allow fan to be set to full speed

[linux-thinkpad@linux-thinkpad.org]

On Mon, 22 Aug 2005, Thomas Renninger wrote:

> Bret Comstock Waldow wrote:
>>
>> Do we know that the fan can operate at these speeds without significantly
>> shortening it's lifespan?

Oh, indeed we don't know that - at the racket it makes, I expect it
puts quite a draw on the battery.  It would probably be something
you'd only want to enable on AC.

>> Does the fan ever run this fast under Windows?  If not, and Windows
>> nevertheless doesn't go into thermal shutdown, then we are missing some other
>> part of the power/thermal management picture, and trying to push the fan into
>> making up for our lack of knowledge.

I totally agree - this isn't a solution, but a patch-up for some other
implementation problem that hasn't yet been fixed (in ondemand, or acpi
in general?) - but it seems like a pretty helpful one for me, anyway.
As someone else indicated, it didn't save their thinkpad from thermal
extinction under intense GPU load, just delayed it significantly -
but my graphics card isn't as powerful :)  I suspect though it's very
useful for those of us who regularly have very hot laps, and just
can't get the temperature down when CPU load is very high for some
time.

My email to Paul Rivier, who wrote the most comprehensive
ibm_manage_fan script (not the ones on the Wiki, unless they were
earlier versions of his) bounced, so I'm not sure he's receiving this,
and my suggestion to add this full-speed option to ibm_manage_fan
at very high temperature.  I however did implement it my own version
of his script, and I'm very pleased with the result - at full-speed
it can render turn my T40 back into an icebox very quickly, albeit
with a spurt of loud noise, and I expect and find this to be very
infrequent (I set the script to go full-speed at 85C CPU, and go down
again at 60C).  I called the variables MIN and MAX_BOILING_TEMP :)

Because the patch sets the fan state as disabled, unfortunately my
version of the script is a bit hacky, and therefore I don't want to
distribute it for fear of a bug melting someone's thinkpad - but
you'll see it's very easy to do yourself if you know any shell
scripting.

But agreed, it's a patch-up while we wait for proper thermal control
- it's just it seems like a very good patch-up for me.  Thanks go to
Thomas.

Honey