Arjan van de Ven wrote: > Alan Jenkins wrote: >> >> AFAIK: The headline figure would be %age time in C4. > > yup > >> I'm thinking the avg residency figure doesn't actually add anything to >> that. > > that's not quite the case unfortunately. > >> Transitioning to/from C4 takes some time, during which power is being >> drawn but no productive work done. However if you spend more time in >> transitions but the same time in C4, all that means is you got less >> time doing productive work; there might be no difference at all in >> terms of power usage. > > transitions are actually quite expensive (well everything is relative of > course); it means analog parts of your chip need to go on or off. Think > of it as with traditional light bulbs; when they turn on they briefly > take a lot more current than when they're fully enabled. > (this is also why they break at this point more often) > > Depending on the cpu type, the time you want to be in C4 ranges from > 20msec to 50msec. (this assumes current cpus; future cpus might and will > vary). Above 50msec you'll not see much power difference today. > > > So the answer to the original question is something like: > * try to get C4 %age above 99% > * try go get average time there above 50msec
Thanks ..... exactly what I was looking for. I guess this would be a good data point that could be added to the FAQ -G _______________________________________________ Power mailing list [email protected] http://www.bughost.org/mailman/listinfo/power
