[Tfug] Dell Laptop & Thermal Shutdowns

[Bexley Hall]

--- "Bill M." <beelymagee at cox.net> wrote:

> I'm having an issue with the system: in times of
> intense, heat-creating activity (running KDE or
> Gnome and loads of eye-candy and processes
> running, lots of hard drive activity, processor
> really cranking, WLAN interface active as primary
> network connection), I've experienced situations
> where the laptop does a preventative thermal
> shutdown with the briefest of warnings. I'm
> thankful that I'm not experiencing motherboard
> melt-down, but it's very annoying! I even use a
> laptop cooling fan base while at home--still
happens.

Your fan (internal and external) can be operational
yet still not doing the job.  Any crud that gets
between the CPU and the airflow increases the thermal
resistance -- think of it as an "insulator" (thermal)
in much the same way that a blanket captures (body)
warmth.

Of course, dust is a prime candidate.  But, laptops
you also see a lot of hair (eyelashes, etc.) and
other crud sucked into the machine (because laptops
often travel *to* the crud whereas desktop machines
have to wait for the crud to come to *them*!)

> I've read that Dell laptops have been notorious for
> their overheating, but I never really had shutdowns
> when I originally ran Windows XP on this (since
> completely removed.) System runs in the mid-60s to
> low 70s normally with the thermal shutdown
> trigger at 78c.

Most (newer) temperature sensing is done on the *die*.
This is VERY responsive to changes in die temperature
(i.e. very low thermal resistance).  The die's
temperature can quickly change with different use,
etc.

Depending on the chip/circuit, this could be
aggravated
by cache *hits* or *misses* (depends on
characteristics
of the bus interface and size of cache... "changes"
in signal levels == heat).

Also, other peripheral power demands can increase
the ambient temperature (which makes it harder to pull
heat away from the device).  And, these loads can
also affect the supply voltage to the CPU, etc.

(bottom line, thermal analysis is nontrivial -- a
real art form -- which is probably why so many
devices have heat problems!)

> The exhaust vents look clean.

They may not be BLOCKED yet you could still have a 
film of dust/crud that reduces the moving air's
ability to carry heat from the processor.

> I've read that it is sometimes necessary to remove
> the keyboard and check/clean out the heat sink

<frown>  You may find yourself going down this road.
But, if you've never had the skin off, be advised
that it is not an easy task on many laptops (lots of
little plastic things that don't like being un-done)

> and even reapply thermal grease between the
> processor and the heat sink.

Unlikely -- unless the machine is old.  Elephant c*m
seems to last forever if not disturbed.

I assume you can monitor temperature in "real time"?
When this happens, can you stop doing "something"
and see if there is a difference?  E.g., maybe
replace the wifi with a wired network interface
(not saying that this is more or less power hungry
but it is *different* and gives you another data
point)

--don

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