Hi, > > I don't have a clue (yet) where exactly all that power goes to, and how > > much of it is actually being used by the stick itself (it's getting pretty > > warm, too - maybe you have a clue what to expect there?). But apparently, > > quite a bit of that increased power consumption is due to the CPU entering > > ACPI sleep states for a much smaller proportion of time, and not entering > > the highest sleep state at all anymore (which otherwise makes up around > > 98 % of the time) due to some polling/high-frequency interrupt of the > > driver. After all, even the most inefficient voltage regulator can't > > make 15 W from USB's max. 2.5 W (I hope ...). > > My RTL8187B does get quite warm. The 'lsusb -v' output says that the > device can draw up to 500 mA or the maximum 2.5 W, but it does seem > warmer than that. That's my impression, too ... but it doesn't feel like 15 Watts, either :-) > > Now, the obvious question is: Is there anything one could do about that? > > AFAIK, the rtl8187 driver is not running any polling loops. It will > interrupt the machine whenever it receives something or whenever data > needs to be transmitted. You could cut the frequency by changing the > beacon interval to 2 s. It is probably now set at 0.1 s. Beacons are sent by the AP only, aren't they? I guess I could try playing with the AP's config. On the other hand, the point of a wifi interface for my laptop is not primarily to connect to my own network ... > > And if not, or possibly even if: Any recommendation for a power-efficient > > USB 802.11 adapter - in particular something that does not cause > > CPU wakeups all the time when there is no actual network traffic? > > Not all network traffic is data. Well, yeah, I meant "payload I care about", of course :-) For comparison, if I plug in and configure my prism2 card to connect to the same AP, power consumption goes up by ~ 2 Watts while idling. Given that it seems to be possible to build a wifi interface (plus driver) that does manage to stay connected on a budget of ~ 2 Watts, I would hope that there is such a thing for USB, too. b-only would be fine, too - it's USB 1.1 only, anyhow. Florian -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
