Garbled PowerBook displays: Caused by problematic memory?

We continue coverage of an issue where various systems display a distorted screen image -- a scrambled version of the expected image or a series of random blocks -- when waking from sleep.

For some users, the issue fades after a few seconds, or can be resolved by simply putting the Mac back to sleep and re-awakening it:

MacFixIt reader Pete writes "My iBook G4 14" 933MHz has the "garbled screen after wake up issue". Sometimes it will go away right away, other times it will go away if I put it to sleep and wake it up again."

Don Donovan adds "I get a very brief 'garbled display' when I awake my screen from sleep (looks like a display window that's been squashed) on my eMac using 10.3.7. It appears only momentarily and everything else proceeds normally. Thereafter. It's annoying but that's all."

Bad RAM It appears that in some cases, this issue can be caused by a faulty or incompatible RAM module.

MacFixIt reader Rick Roberts writes:

"I had the same issue with my 12" PowerBook. [...] My PowerBook came with a 'free' 512 MB RAM chip. After finding a reference to the problem in the Apple Discussion forums, I removed the chip and the problem went away (along with the kernel panics I experienced twice). After working on the base 256 MB module for two days, without seeing the problem, I put the memory chip back in the PowerBook. The screen issues came back immediately.

"I contacted the vendor, PC Connection, they shipped a replacement stick overnight. I installed it and have not had a screen problem or a kernel panic since. The stick came from the same company, but it's obviously from a different batch. The profile of the new stick is lower and looks like it came from a different factory."

Triggered by incremental Mac OS X Updates (including 10.3.8) In other cases, it appears that incremental Mac OS X updates are direct or indirect causes of this issue.

MacFixIt reader Michael Comins "As soon as my download of OS X 10.3.8 concluded, I woke my Powerbook G4 to restart and immediately saw the garbled display."

Since successive incremental Mac OS X updates have been known to be progressively more "picky" about RAM, this notion reinforces notes from a number of readers (as mentioned above) that removing certain modules can resolve the problem. If possible, try removing all modules except for those initially shipped with your system, and re-check for the garbled display after wake-up.

Feedback? Late-breakers@macfixit.com.

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