I’ve recently been having some kernel panics and rebooting/crashing on my MacPro 1,1 running 10.6.8 and Lion and some suggested it could be my CPUs overheating. There was a suggestion to install SMCfancontrol and run all fans and a higher speed and keep an eye on temperatures whilst stressing the CPUs to 100% for a prolonged period. So below is a little bit on info on how to crank your CPU up to 100% usage and monitor core CPU temperatures.
Getting you CPU to 100%
There are several ways to max out your CPU, some suggest ripping movies using Handbrake or re-encoding your music library but personally I don’t want all the faff with that plus these methods are IO intensive for your hard drive which isn’t good. All I do is open up Terminal (Applications/Utilities/Terminal) and then once it’s opened type
yes > /dev/null
and hit return.
That should max out 1x core. Then open a new terminal window (CMD+N) and again type
yes > /dev/null
and hit return. Again this will max out another core
Keep on repeating this process until all your cores are maxed out.
To keep an eye on CPU usage open Activity Monitor (Applications/Utilities/Activity Monitor) and look at your CPU history to see if they are all maxed out.
You can then leave this running for as long as necessary in order to run your CPU at full load and monitor temperatures and fan speeds.
Monitor CPU core temperatures
Viewing your CPU A and CPU B temps using iStat Pro widget or similar is not that accurate or useful as it’s reading the temperature from the heatsink not the actual cores of the CPU. if you want the most accurate temperatures you need to use an app that shows individual core temperatures. I use Temperature Monitor for OS X which is free and even has history windows so you can view the core temperatures over a period of hours or days.
NOTE – To cancel the stress tests on your CPU simply close all the open terminal windows (CMD+W) and/or quit Terminal (CMD+Q).