Windows System
Processor Throttling In Windows XP
A summary of Windows XP power schemes as they relate to Intel processor throttling. Old topic, but one still relevant as many business notebooks still use XP.
In Windows XP, you can access the power profiles by going to Control Panel -> Power Options -> Power Schemes. There are a number of Windows XP built-in power schemes and from this user interface, it’s easy to assume that’s the only difference between each of the power schemes, but in truth there are hidden meanings to each setting when it comes to how the processor is programmed to react to different loads (computing tasks).
Now, looking at this table, one could assume that “Minimal Power Management” & “Portable/Laptop” 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.
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.
Anyway, you can use the following command from the Windows XP command line (Start -> Run… -> cmd) to look up the settings of any power 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 (all in one line - not two):
POWERCFG.EXE /CHANGE Portable/Laptop /processor-throttle-dc CONSTANT
