iCook

Download iCook

iCook is a small OS X kernel extension that allows simple overclocking of the IBM 750FX processor found in some Apple iBooks. It should be compatible with all iBooks that have more than 16 megabytes of video RAM, but not the new iBook G4s. At this time iCook requires OS X 10.3 or higher, however this will change in a future version.

I first read about this feature of the 750FX in this article at xlr8yourmac.com. Since then Apple has made it more difficult to change the iBook's speed. It seems that current versions of OS X continually monitor the CPU speed and set it back to normal if it is changed.

iCook gets around this by patching the kernel image in memory to disable it's ability to set the CPU speed. It then sets up a sysctl called hw.cpuspeed that allows the CPU speed to be set and monitored by the user. iCook makes no permanent changes and everything goes back to normal after a reboot.

I am able to run my 700 MHz iBook at speeds from 300-800 MHz, although 800 MHz is not entirely stable. CPU performance scales nicely along this range as can be seen in this graph of results from Apple's Skidmarks GT benchmark. iCook allows speed settings from 300-1200 MHz in 50 MHz increments and comes with the full GPL'd source code.

For more information see the ReadMe file.

Quick Start Guide:

1. Open System Preferences from the Apple menu and click on Energy Saver. Under the options tab ensure that Processor Performance is set to Highest for both the Power Adapter and Battery Power modes.
2. Now download iCook.
3. After the transfer is done unzip the archive and run the "Install iCook.pkg" file to copy the iCook kernel extension to your hard drive.
4. To use iCook you'll have to get to a command prompt by running the Terminal program which can be found in /Applications/Utilities/.
5. Load iCook into the kernel by typing "sudo kextload -b net.swieskowski.iCook". If this fails you probably do not have a 750FX CPU.
6. Now you can check your current CPU speed by typing "sysctl hw.cpuspeed".
7. You can set your CPU speed with a command like "sudo sysctl -w hw.cpuspeed=800". Just replace 800 with the speed you'd like to set your processor to.
8. After a reboot your system goes back to normal with OS X managing the CPU speed. To use iCook again just repeat steps 4-7.

Because iCook disables OS X's ability to change the CPU speed the Processor Performance settings in the Energy Saver System Preferences will not work after the iCook kernel extension has been loaded. They become active again after the next reboot.

Some good reading on the 750FX processor can be found at IBM's documentation page for it. Of particular interest are the 750FX Datasheet, 750FX User's Manual, and the PowerPC Programming Environment Manual.

	26-06-2008 13:49
	how to do this in os 10.4.11 ??? Guest

boki

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