Hi,

In case you didn't stumble upon it already, I suggest strongly suggest
reading the latest entry from Julien Blache's blog, who brings up quite
crucial issues in macbook support. Though his observations are based
upon a Pro model, I guess it applies to the whole macbook line.

Due to the severity of this issue (which not only affects battery life,
but probably laptop life as a whole), it would be nice to see some
further brainstorming, not to mention reverse-engineering, if possible.

----- >8 -----

Taken from http://blog.technologeek.org/2006/12/27/44:

[...]

- Battery life: no news here, 1h30 is the max you’ll get. You need to
  suspend to disk if you want to swap the battery, it’s not possible to
  do that in suspend to ram like it was on the PowerBook (G4 500, at
  least). Sad.
- Heat/fan noise: catastrophic. Fans running at 4000-4200 rpm on a
  typical desktop or on my laps, down to 3000 rpm on a glass desktop.
  More on the SMC below.

[...]

In a previous post, I was reporting a lot of timeouts from the applesmc
“driver”. After a (very) quick look at the AppleSMC kext for OS X, I
know why this happens. It looks like the OS X driver uses an interrupt
and configures the SMC for that. So it probably doesn’t poll the SMC 20
times per second like the applesmc “driver” does.

It also looks like the OS X driver uses SMC keys we know nothing about.
I could also confirm that the SMC has access to temperature sensors for
the CPU, GPU and memory, but it looks like we have no idea of the
corresponding SMC keys.  With this information, it’d be possible to
switch the SMC to manual mode with a userspace governor.

What probably happens when we run Linux on this machine is that the SMC
stays in automatic mode, and it’s very conservative in this mode. It
won’t hesitate to run the fans at high speed to keep the machine safe.
It is highly probable that the OS X driver is taking over the fan
control to keep the machine both cool and quiet. This is mostly
speculation, as the better device power management in OS X plays a role
too, and the SMC could very well still be in automatic mode under OS X
keeping the fans at low speed just because the machine generates way
less heat.

Unfortunately, the AppleSMC kext isn’t released as part of Darwin, so
we’ll have to wait until it is. Could be a long wait, though.

The SMC handles a lot of things. I don’t feel safe running an OS without
a proper driver for the SMC on this machine. The fans probably aren’t
designed to run at 4000+ rpm for 3 years and will probably fail early or
something. 

----- 8< -----

-- 
mike dentifrice <[EMAIL PROTECTED]>


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