Some users are not aware of the issue until they check the "About This Mac" pane accessible via the Apple menu or experience significant slow-down in a particular application.
The first course of action if you are experiencing this problem should be to re-seat and or swap RAM modules. That is, first remove any RAM modules from your machine, then re-insert them ensuring a snug fit. Failing that, try switching the slots in which your modules are installed.
In other cases, performing a set of open firmware reset routines can result in the memory being properly recognized again.
To boot into Open Firmware, shut down your Mac, then start it up while holding down the Command, Option, O and F keys. At the prompt, enter the following commands (you may want to write them down on a piece of paper before beginning this process), pressing the return key after each:
after which your Mac will restart.
Note also that incremental Mac OS X updates can introduce RAM recognition problems, sometimes resolved by the aforementioned workarounds or reversion (downgrading) to an earlier version of Mac OS X.
Unfortunately, these routines are not always successful, and faulty hardware components -- particularly logic boards -- sometimes need to be replaced.
More than a year after the issue was reported, Apple began offering the "Memory Slot Repair Extension Program" (as reported here). The program covers repair or replacement of the memory slot in PowerBook G4 models manufactured between January 2005 and April 2005 (2005-01 through 2005-04) outside of normal warranty. Apple says the following symptoms are indicative of replacement candidacy:
- The computer does not start up; instead, there are three short beeps (typically) followed by the the sleep LED flashing periodically.
- When both SO-DIMM memory slots are filled (populated), only one slot's memory is recognized.
- System performance may be degraded because the memory in only one slot is not recognized.
The predicament with the repair program is that Apple has only admitted to flaws in PowerBook G4 15-inch 1.67/1.5GHz systems that have eleven-digit serial numbers in this range:
- W8503xxxxxx through W8518xxxxxx
Finally, some users have had success with other repair services that are re-soldering RAM contact points:
MacFixIt reader Ernest Leitch writes:
"I was referred to DT&T services. I sent my powerbook to them and they fixed it for about $300. The problem is the solder points on the module become weak and break. They can re-solder the points and it will repair the slot and it's much cheaper then replacing the logic board."