The other day I stumbled upon a bug that caused my CPU to run excessively and produce extra heat. If you see similar symptoms in Activity Monitor, you may be seeing the same thing. I don't have the same problem with my Power Mac G4 (also on Tiger 10.4.6), but maybe it's common on the Macbooks?? I'll try to be concise in my description so you can skip the rest of this if it doesn't apply to you. Starting the other day, my Macbook began using about half of all available CPU (1 full CPU out of two) constantly, causing a significant rise in temperature. The really strange thing was that the process list in Activity Monitor showed less than 10% of one CPU being utilized, or less than 5% of all available CPU. It was like a ghost was using my CPU! To check for the same thing, open /Applications/Utilities/Activity Monitor. Set it to show All Processes and sort by the CPU column. Look at the CPU tab along the bottom and check the reported CPU usage versus what you see in the CPU column above. If yours looks like mine, maybe you have the same issue. In the screen shot above, I have 5.8% of one CPU accounted for in the process list, but a total of 53% of both (106% of one) used in total. This happened shortly after installing a few updates, including QuickTime 7.1.1, Developer Tools 2.3, CoreDuoTemp, and Parallels RC2. I tried uninstalling each of these (except the QuickTime update) with no luck. No matter how many times I rebooted, the CPU usage came back within 15-20 minutes. What could possibly be using CPU without showing up in the process list?? It made no sense. Until it hit me that if dozens or hundreds of very short-lived processes were created and destroyed, any single one of those would never run long enough to show up. Aha! I used 'ps' from the command line to search for recent short lived processes, and sure enough there it was: nmbd kept getting restarted about a dozen times a second. Here's where my Unix experience really pays off. I know that nmbd is part of Samba which provides Windows file sharing services for OS X. Solution: In System Preferences, turn off Windows Sharing. CPU usage immediately went to near zero. A perusal of the nmbd log (open /Applications/Utilities/Console, click on Logs, /var/log, samba, log.nmbd) confirms that nmbd keeps exiting because it can't bind to the right network port. So now I'm armed with the info I need to send in a bug report to Apple. What's interesting is that launchd is responsible for starting nmbd. I believe that launchd is supposed to listen on the network port that nmbd wants, and therefore nmbd is not supposed to even try to open it. Not sure if it's a bug in launchd or nmbd then. However, even so, launchd should throttle back and wait (5, 10 seconds, a minute, whatever) when the process it's starting exits so quickly. Anyone else see the same thing?