[ltp] Re: ThinkPad Batteries

[Michael Karcher]

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Am Dienstag, den 18.11.2008, 01:54 +0200 schrieb Micha:
> > Nothing is stored in the battery.
> Makes sense but still, those thresholds hold even if I charge the compute=
r when
> it's off. I can turn it off, charge it while it's off and it still doesn'=
t go
> above the set 80%.
If you turn your thinkpad off, the EC does *not* turn off as long as AC
is present. It seems to be common knowledge that on modern Thinkpad, the
EC even stays on as long a battery *or* AC is present, so your 80% value
keeps active unless you drain your battery to exhaustion (you should
avoid that anyway) or let it alone long enough with any power source.

The EC is *not* part of your BIOS that does things behind your back,
this is called the SMBIOS (and accessed via smapi), but a tiny low-power
processor that works completely independent from the main processor, and
handles at least the following things (on a T20, T60 might be different)
 - Keyboard controller
 - Keyboard processor for the internal keyboard
 - Communication with external PS/2 keyboard if present, synching
indicator lights and things like that
 - Communication with Touchpad, Trackpoint and external PS/2 mice.
 - Hardware volume control
 - Brightness control
 - Controlling the LEDs
 - Controlling the fan
 - Supervising battery charging and selecting batteries if more than
    one is present (THIS is what we talk about)
 - Handling the bay-eject handle.
 - Handling the docking process.
 - Thermal supervision, shutdown of the system if way too hot.
 - Beeping signals (for example on critical battery), this does NOT
   include the usual PC speaker beeping.
All these things are completely independent from the host processor,
even if the EC stops performing may of the tasks when the host processor
is not running.

Regards,
  Michael Karcher

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