Existing users, 
AppleJack
troubleshooting tool that runs in single-user mode
Version: 1.5
iMac G5 stuck on Highest Processor Performance
Feedback Type: Commentary
Contributed by: jeffulri Sunday, November 13 2005 @ 09:32 AM PST
Product Platform: MacOSX
Used Product For: Over One Year
After using AppleJack on an iMac G5, Processor Performance becomes stuck on Highest (regardless of your settings in Processor Performance) [You know, the fan ramping up and STAYING that way]. I have reproduced this problem, so I KNOW it wasn't a one time thing. It is ONLY fixed (and yes, it isn't fixed by changing the .ktext file, resetting permissions, or any other hooey you may have heard about) by PHYSICALLY resetting the PRAM/NVRAM hardware switches (IE: Opening up your iMac). A software fix would be nice. Aside from this, the software performs as described.
Comments
iMac G5 stuck on Highest Processor Performance - donrichardsoth
Had the same problem with iMac G5 - your solution (unplug) worked for me too.Thanks for the tip . . .
Tuesday, December 27 2005 @ 10:43 PM PST
iMac G5 stuck on Highest Processor Performance - tersonodesign
Yup - it occasionally happens on some G5 towers too - I've seen it on several occasions. In all fairness, it's NOT down to Applejack, just a glitch in the way that system cooling is handled by the hardware when the software controller isn't running. Unplugging for a few seconds solves the problem.Wednesday, January 04 2006 @ 09:50 AM PST
iMac G5 stuck on Highest Processor Performance - schreibmal
I have also had the same problem with the fans in a G5 iMac going beserk after running Applejack. My solution was to unplug the power cable for about 30 seconds. Not sure what is going on here, but otherwise Applejack is a wonderful tool at an unbelievable price!Reply to This
Wednesday, November 30 2005 @ 12:23 PM PST