Usually when troubleshooting problems there is some logical reasoning behind the issue that can be readily tackled, which is indicated by a steady, observable problem with the system. Even if the solution to the problem is a broad approach, such as reinstalling the operating system or replacing a hard drive, the reconfiguration usually clears the issue and the problem goes away. Despite this, every now and then a problem will crop up that is fairly perplexing.
We were recently contacted by MacFixIt reader Alan, who had a relatively minor though annoying problem where his system would crash under specific conditions when waking from sleep.
Normally when a Mac is put to sleep, it can be woken at any time to restore normal function; however, in Alan's case, his Mac (a mid-2006 Mac Pro model with fully updated firmware) would crash after being woken from sleep, but only if the system was woken after a few minutes in sleep mode. If the system was left in sleep mode for longer than a few minutes, it would wake up perfectly fine and continue running.
We tried a number of approaches to addressing this issue, including the following:
Reset PRAM and SMC
Boot off an external boot drive
Booting off an alternative minimum OS installation set up for diagnostics and repair
Running full hardware diagnostics using TechTool Deluxe
Having full hardware diagnostics done through Apple Care servicing
Removing all add-in cards and peripheral devices
After all these attempts, the system still shows the same behavior: only crashing when woken within a few minutes of being put to sleep. Despite this problem, the computer otherwise works great and shows no odd slowdowns or other crashes.
The only remaining possibility that comes to mind for this situation (and this would just be a guess) is some fault in a hardware component, be it a capacitor or other physical component, where waking from sleep requires it to be in a state that it only gets to after a few minutes of being powered down. In this case, waking too early results in the system trying to make use of it when it is not ready, and thereby causes a conflict. As a result, since all the other attempts did not work, there are several options:
Replace hardware components
Even though the hardware in the system checks out with diagnostics, since three separate OS installations show the issue and firmware is up to date, this issue is likely in some hardware component. If needed, then replacing components would be the next step (motherboard, graphics card, etc.).
Deal with it
Since the problem is a regular and predictable issue, another approach is to just let it be and be sure to never wake the system during its "down time."
Never use sleep again
Go to the Energy Saver system preferences and set the system to never go to sleep. This will bypass the problem, though it will ultimately use more energy in the long run and is a mere workaround instead of a fix.
Have you had similar puzzling experiences in the past? Perhaps you have a suggestion for an alternative approach to this problem. If so let us know in the comments.