[ltp] How to disable unnecessary hardware

[Richard Neill]

>> How do I disable unneeded hardware to save power on my Thinkpad X60:
>> 1) Infrared port
>> 2) Modem (no linux driver installed)
>> 3) Firewire / 1394
>> 4) SD host controller may be
>>
>> Disable in BIOS? rmmod? some setpci magic?
>
> best in BIOS if disabled there, it will powerdown the devices so
> linux/windows will not see them anymore.
>

It would be interesting if you can do some experiments to discover the 
difference between:
    - disabled in BIOS
    - rmmod
    - power optimised in powertop
    - normal (idle).

Try running on battery, and after 1 minute of leaving the system 
quiescent, do:
  grep rate /proc/acpi/battery/BAT0/state
(This is a recent aaverage, not instantaneous).

My suspicion is that the idle peripherals use relatively little power, 
compared to the huge drain from the backlight (and the Wifi, CPU, 
motherboard, HDD and RAM)...but some data would be interesting. After 
all, saving 10 mA isn't really worth it, but 100 mA would be.

BTW, the fingerprint reader used to be known to be problematic: it was a 
USB 1.0 device, without power-management capability. I fixed the one on 
my T60 by simply unplugging its (highly accessible) ribbon cable. The 
X60 may not be as easy to get at though.

HTH,

Richard