Re: Overheating is *not* dangerous Re: Changing temperature trip points

Pavel Machek
2002-11-03T22:46:34Z

Hi!
> > > > Actually, Documentation/acpi/processor.txt seems like right
> > > > place. "Polling" warning should be in Documentation/, really.
> > >
> > > Which does not exist ==> extremely dangerous situation. Even though you
> > > should know what you're doing when you meddle with the affairs of kernels,
> > > kernels should try at least to some extent to be safe to use.
> >
> > So perhaps its good time to create Documentation/acpi? ;-).
> >
> > Anyway it is not *dangerous* situation. ACPI machines power down on
> > overtemp.
> ACPI machines power down on overtemp. What is overtemp? The temperature
> specified in CRITICAL in the DSDT. And if this value is wrong, then you need
> to rely on the sanity of BIOS programmers. And a log of good luck.

Actually, I believe its sanity of HW designers. I'd not trust BIOS
programmers to get it right.

There's one more point above _CRT, that's what I call overtemp:

[from specs:]

This says that if you can cook your machine, it was not acpi
compliant.
Pavel

When the heat reaches the temperature indicated by _CRT, the OS must
immediately shutdown the system.
The system must disable the power either after the temperature reaches
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
some hardware-determined level above
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
_CRT or after a predetermined time has passed. Before disabling power,
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
platform designers should incorporate
some time that allows the OS to run its critical shutdown
operation. There is no requirement for a minimum
shutdown operation window that commences immediately after the
temperature reaches _CRT. This is
because
* Heat might rise rapidly in some systems and slower on others,
depending on casing design and
environmental factors.
* Shutdown can take several minutes on a server and only a few short
seconds on a hand-held device.
Because of this indistinct discrepancy and the fact that a critical
heat situation is a remarkably rare occurrence,
ACPI does not specify a target window for a safe shutdown. It is
entirely up to the OEM to build in a safe
buffer that it sees fit for the target platform.

--
Casualities in World Trade Center: ~3k dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.