I followed a link from that article to
http://www.androidpolice.com/2013/1...-in-secret-for-over-2-years-debuts-in-kitkat/ which had this:
Additionally, now that the typical device contains a quad-core (or greater) processor, many situations will call for activating fewer cores, and it may be possible to make even better use of the lower-powered cores in ARM's big.LITTLE architecture. How much this improves battery life and performance will vary quite a bit based on usage scenarios and hardware, but the results could be substantial.
That got me thinking, because I've already been trying to do some battery comparisons between normal mode and the standard power saver mode with the CPU power checked and also locking mobile data to 3G by turning the LTE radio off. Despite performance testing pointing to the CPU throttling being accurate, I wasn't seeing much of a difference in battery times. I'd say 30-45 min extra on battery from a full charge with power saver on. Maybe an hour if I stretched it and lightened my usage.
So I downloaded the CPU-Z app and checked my clock speeds. With the phone basically at idle, only Core 0 was running, and Cores 1-3 were reporting "stopped." (See screenshot). So it sounds like the regular power saver function will be almost useless unless you're doing gaming or something that would normally max out all 4 cores. Anyone still on Dalvik care to run CPU-Z too to see if it runs all cores even if idle to maybe confirm this?
One odd thing I did notice was even when running BOINC with four tasks running (1 per core), the CPU wouldn't throttle up over about 1.25GHz each in normal, un-throttled mode. I checked my BOINC settings and the app doesn't seem to be throttling itself that way. So I'm not sure if it's something hard coded into the app, or a quirk related to ART. When churning, the phone is set next to my A/C vent anyway, so I've got the thermal head room to crank up the CPU while still keeping cool. Going by heat alone, I'm pretty sure the CPU is able to ramp up much faster and it's not a defect on mine. The phone gets much hotter playing Asphalt 8 than running BOINC.