On 10/13/2013 9:22 AM, Marc MERLIN wrote:

>> having a USB device active also generally makes the CPU/etc use much more power,
>> which Powertop "charges" to the USB device in question.
>>
>> 8 Watts sounds entirely reasonable for that to me...
>
> Aah, if the CPU gets involved, then yes, it's a bit more possible.
> So, a simple USB keyboard that's unused can keep one core awake and burn 8
> watts if something else goes wrong in the kernel to cause that?

a bad USB keyboard can keep the processor out of deep package C states..
not a lot the software can do about that...
but yet it can be THAT much power delta.

(we've seen for example on some servers that a cheap keyboard makes > 15 Watts difference, but measured
at the wall socket, so after the power supply/etc)