Today’s post is going to be a bit specific, however it helped me solved a long running problem where you Mac would freeze / hang after waking up from sleep, freezing during normal use and it randomly freezing through out the day. It was a real pain, however, I managed to solve the problem due to the switching of the graphics card in my MacBook Pro. Although this may not solve everyones random freezing problem, it may help those in specific circumstances where there MacBook would hang for no reason.
The Hanging Issue
Your Mac may hang for a variety of issues, some may be hardware related such as a corrupt hard drive, or RAM. Others may be software related such as an unstable kernel release or a dodgy app interrupting everything. My solution was down to the two graphics cards found in my MacBook Pro. In everyday use the low wattage internal graphics card was used, then as the power needed turning up the bigger better dedicated graphics card kicked in. This means that I get good battery life when I am surfing the web and a good amount of power when I am playing games.
At some point there needs to be a switch. Your Mac is pretty good at doing this, however I found when I upgraded to Mountain Lion the freezing issue appeared. It would randomly hang when I woke from sleep, or when I was surfing the web. It happened randomly throughout the day.
The problem originated when I was looking through the console. Located in Applications > Utilities. Under ‘All Messages’ and system.log the following would appear:
kernel: AMDCaicosGraphicsAccelerator: ** Device in slot: SLOT--1 **
kernel: ** GPU Debug Info Start **
kernel: ** GPU Debug Info End **
kernel: GPU hang: Not Implemented
kernel: Trying restart GPU ...
com.apple.launchd (com.apple.DumpGPURestart): Throttling respawn: Will start in 4 seconds
This would appear at the same time of the freeze. The mouse would not move, no keyboard entries could be made, the clock would not update. A full system freeze. The only solution was a hard restart.
The solution to this problem was rather simple. Turn off graphics switching, then turn it back on at a late date. This disables the graphics switching option, causing the hang not to occur. I then later turned it back on with no ill effects.
To turn off graphics switching open System Preferences and click on Energy Saver. At the top of the preference you will notice an option that controls the graphics switching. Turn this off.
Immediately the graphics hang option stopped.
When you are satisfied that that the graphics switching and hanging issues has stopped you can turn the graphics switching back on. I have had a happy non-freezing Mac for many days.
It is only a simple change, switching something off and on again. But it solves a deep problem. It may not work for you, but it may be a solution for others. I had graphics switching turned off for a week and when I turned it back on I had no ill effects.