[Debian-eeepc-devel] PCIe ASPM?

Thiemo Nagel thiemo.nagel at ph.tum.de
Tue Jul 21 21:44:15 UTC 2009

Darren Salt wrote:
> I demand that Thiemo Nagel may or may not have written...
>> has anybody thought about including PCIe ASPM?  Saves roughly 0.3 Watts 
>> on my Eee PC 1000HGO.  How about lumping this together with S.H.E.?
> Could do...
>> 0	performance
>> 1	default
>> 2	powersave
> Older EeePCs with just the two S.H.E. states need to have one of those
> omitted; I'd omit "performance".

I wonder, whether really substantial savings are achieved with ASPM. 
When I use a more rigorous approach to measure power consumption, the 
0.3 Watts in savings that I've quoted previously cannot be held up.  To 
the opposite:  The "powersave" mode seems to use ~0.1 Watts more than 
the "performance" mode.

I've attached my script which does a stochastic comparison of power 
consumption of two different configurations (currently with and without 
ASPM):  It's measuring (and averaging) power consumption while randomly 
switching to and forth between both configurations to get an unbiased 
sample.  (That means that one can use the computer normally without 
disturbing the measurement.)  I'd be interested what results other 
people get on different machines.  (The most interesting value is the 
"tot. avg" for the two different configurations, the number of 
measurements "n" should be above ~100 for a good average.)

Another strange thing:  From time to time, I'm seeing bursts of very 
unreasonable current and voltage readings, like in:

Ignoring unreasonable reading: C=1413000uA, V=37008000uV
Ignoring unreasonable reading: C=37008000uA, V=37008000uV
Ignoring unreasonable reading: C=37043000uA, V=7494000uV

powertop is getting these too, occasionally reporting >1000W of power 
consumption.  Hardware bug or kernel bug?  I'm running 2.6.31-rc3 on Eee 

Kind regards,


| Dipl.-Phys. Thiemo Nagel          |                          |
| Technische Universitaet Muenchen  | Room    PH1 3276         |
| Physik-Department E18             |                          |
| James-Franck-Strasse              | Phone  +49 89 289-12379  |
| D-85747 Garching                  | Fax    +49 89 289-12570  |
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