Turn off additional cpu cores while on battery

Question

I'm currently an running a quad core processor on windows 7 and was wondering if there is a way to turn off unneeded cpu cores while I'm running on battery to extend battery life it would be nice to do this automatically but will also accept way to it manually if there is no way to do it automatically either in windows or through management software I've searched on the internet and haven't been able to find anything to this effect on google

Answer 1

Which CPU exactly do you have? Recent Intel CPUs, for example, have a dedicated Power Control Unit (PDF) which automatically turns CPU cores on/off in response to demand. In general, this is called power gating, where circuits are completely de-energised when not needed. Intel introduced this with their Nehalem architecture, and AMD has announced plans for an upcoming "Llano" CPU/GPU chip. This is in addition to automatic clock frequency scaling which has been around for longer (such as Intel's SpeedStep). If you really wish to have control of the CPU's power consumption, it may be easiest to underclock the CPU multiplier; you may be able to do this in the BIOS, and possibly using software from within Windows.

However, I'd assume that the CPU engineers thought about the problem in great detail, and that the CPU - by default, especially if it's a recent model - provides a good compromise between processing speed and power efficiency.

Answer 2

Go have a look in the energy saving control panel. In the advanced part you will find a plethora of preferences that you can tweak to your hearts content. However, I am not quite sure if it includes shutting down cores. (This might be a special driver feature or something that is not exposed in the control panel)

Answer 3

I'm not sure about automatically, or indeed Windows 7, but in Vista the following will work as a manual method:

Start Menu - msconfig - select the Boot tab, then click Advanced.

Set number of processor cores to the amount required and ensure that Detect HAL is selected. Click OK. Reboot.

The only thing you might find is that a processor core uses almost naff all power if it's idling. If it isn't idling then reduced cores may end up taking much longer to complete a task, and use almost as much power.

If your (laptop?) allows, you would do better to fine tune to processor core voltage. Better still, set the maximum power state in power options to a reduced amount (say, 50%).