laptop battery

Now, looking at this table, one could assume that “Minimal Power Management” & “Portable/Laptop” Sony laptop battery and “Presentation” & “Max Battery” are redundant. From a processor point of view, each pair is exactly the same, but the options for hard drive turn off, monitor turn off, and stand by differ. It’s also interesting to note that there’s no way (by choosing one of these schemes) to simply put the processor in its low performance state without it getting slower and slower. Having worked with battery life on notebooks with Centrino Mobile Technology for three years of my time at Intel, it still irks me that people (like Microsoft) don’t think we (as in Intel - I know I left almost two years ago, but after almost seven years of being indoctrinated to think like an Intel corporate citizen, the “we” is hard to avoid) know what we’re doing. In any case, there is ample evidence that if you’re using your machine for business Sony VGP-BPL2 battery activities (that pretty much includes most people - the big exceptions being gamers and 3D modelers), then you want the processor driver to intelligently use Intel SpeedStep to control your processor speed. The power advantage of running at low performance (and having the OS additionally throttle the performance by halting the clock more and more) doesn’t really by you that much more battery life. So, I usually recommend everyone to just switch to “Portable/Laptop” and alter the power down times to their own personal liking.

If you have other power schemes listed, then these were made by someone other than the Microsoft Windows XP installation. For example, my Dell Inspiron Sony PCGA-BP71 battery comes with four more settings called: Maximum Battery (QuickSet), Maximum Performance (QuickSet), Presentation (QuickSet), and Custom Setting (QuickSet) - none of which tell me what mode the processor will be operating in. You can also make your own power scheme by using the “Save As…” button - the processor mode will be determined by the power scheme you started with. For example, if you changed the settings of “Portable/Laptop” and then hit “Save As…” to make your own scheme, then your scheme will also have the processors changing their performance levels to match the tasks you’re running on your computer Sony PCGA-BP4V battery.

Advanced
There is a command line tool that lets you find out (and even alter) the performance mode of your CPU(s) as related to each power scheme. POWERCFG.EXE allows you to look up specific power scheme settings and change them from the command line. It actually does a lot, but I’ll only discuss the Intel SpeedStep technology related aspect. To understand this tool, I need to also explain how Microsoft chose to name the various possible performance settings for your processors - which of course were different than what we called them within Intel Sony PCGA-BP2V battery (at least in my group).

What the processor does Microsoft’s nomenclature What we called it in Intel
CPU(s) run in highest performance state None HFM (Highest Frequency Mode)
CPU(s) intelligently select a performance state based on demand Adaptive Adaptive, SpeedStep
CPU(s) run in lowest performance state Constant LFM (Lowest Frequency Mode)
CPU(s) begin in lowest performance Sony PCGA-BP2T battery state and then get slower and slower via software manipulation Degrade Why are they doing that?!

One of the oddities was that Microsoft clearly didn’t trust that Intel had done their homework and selected a LFM that resulted in the lowest reasonable power consumption. Does throttling the processor even more help save power? Not really - maybe a few more drops could be squeezed out, but the response and performance of the processor is noticeably compromised through their wonderful “degrade” technique.

Anyway, you can use the following command from the Windows XP command line (Start -> Run… -> cmd) to look up the settings of any power Sony PCGA-BP2S battery scheme (even ones that Dell made for you…):

POWERCFG.EXE /QUERY power-scheme

where power-scheme is the name of the power scheme you want to inspect (like Portable/Laptop).

You can use:

POWERCFG.EXE /LIST

to list all the power schemes currently on the machine.

From the query output, the lines starting with “Processor Throttle (AC)” and Processor Throttle (DC)” will tell you what mode the processor will be in when the laptop is plugged in (AC) and on battery (DC). To change the setting, you use the /CHANGE parameter. For example Sony PCGA-BP2R battery(all in one line - not two):