This is a rather cool trick that I stumbled upon today by accident. It is a rather simple, Terminal free way, of disabling (and then re-enabling) CPU cores on multi-core CPU Mac’s. Its rather a neat little trick that for me has been pain free. Normally if you want to switch off a core you would have to run a certain Terminal prompt, and possibly restart. This is then usually followed by the kernel going “What the F*&K where’s my CPU core gone!” and prompting exhibiting a kernel panic. Not good.
If you want to access this tool you first need to install the developers tools. I am not sure which installation packet this little tool belongs in. So install them all (the tools are great anyway). If you don’t no how to install the developers tools. Insert the CD navigate to the extra installs, and follow the folders through until you get to the main installer.
The next step is to navigate to Library > Application Support > HWPref > CPUPalette. You will then see the following application. Click the small oval shaped button in the top right to access the preferences.
To disable a core, press that little minus (-) arrow in the bottom right. The core will then switch off. Technically it is not off. There will still be power going to the core. But it is great for developers who need to test applications on one core. Of course if you have a 16 core Mac Pro, you could switch all 15 off. There are a couple of advantages of switching a core off. You probably will save a little bit of power, but not a lot. On the other hand you could actually use more battery life (on a laptop) or more wall power by using one core. This is because you lose the efficiency of two cores, the performance (sinces apps have to wait longer to run). As well as this fact that the core is still live, its just not allowed to be execute any code. This means a greater draw of power. From researching this you may experience kernel panics or instability. Although I have not experienced any of this. Your adventures may differ.
I said at the beginning of this post I stumbled across this idea by accident. From a post by TAUW, mentioned about the eject menu in the menu bar. Although a cool trick, (I wish I found it) I kept playing with the other menu items. One of the items being CPU.menu . If you double click on this file it will load a menu item with the ability to switch on and off cores. This is how I originally found this trick. It actually uses the same program as the one just mentioned. I think along the lines of development some one forgot to program the link between the two.
CPU.menu is a bit temperamental. For example you can double click on the menu item in Finder and nothing happens. Nine out of ten times this happens to me (hence no screen shot). Every so often (after clicking it) it may randomly appear in your menu bar. As well as this iStat Menus either closes or refuses to reload, meaning you have to restart. This is probably a bug in the menu’s code. I have only managed to get this to work once and then I didn’t notice it was there until sometime after.
If you have any experiences with this program of disabling CPU cores leave a comment below. As mentioned you have two ways. The program way, which works 100% of the time. Or the menu bar way, which never seems to work.