G4 processors were used in many popular Macintosh desktop and laptop models between 1999 and 2006, before they were replaced by G5 chips in desktops, and later, Intel chips in both types of computers. Some of these models had recurrent issues with RAM memory chips, but any computer can demonstrate this kind of issue.
RAM memory is the storage used by the computer in operation; it is distinct from hard drive memory, which is used for longer term storage. These terms are frequently confused, especially since the hard drive can be used to augment internal memory; in general, RAM memory must be in perfect working order, and the more, the better.
A failed memory chip will frequently result in a computer which is unable to boot. Memory chips are solid state (i.e., they have no moving parts), so there may be other telltale signs that the computer’s problem is memory: a computer which consistently fails after a certain amount of time, for example, may be heating its internal chips to a failure point. However, a computer which fails after a particular operation (for example, opening a particular application) is more likely to have an operating system or hard drive error than a memory problem.
If your G4 has more than one memory chip installed, shut down your computer and remove all of its memory. Reinstall the chips one at a time and reboot, to determine if a single chip has failed. If the computer fails to boot with one of the chips installed, reinstall the others to see if the computer remains stable with these chips. A failure in a single chip will make it appear as if they are all faulty; this process will let you determine if any have failed.
4. Motherboard and Chip Slot Issues:
Some models of PowerBook G4s had known manufacturing problems with their memory slots, or the pipeline between the slot and the motherboard. Unfortunately, the extended repair warranty for these models has ended, but you may be able to accurately diagnose the problem with the assistance of the technical support at an Apple Store, who can then direct you to an out-of-warranty repair if necessary.
Hard drive problems are frequently misdiagnosed as memory problems; when a computer completely fails to start up, for example, it is impossible to determine which component has failed. In general, as a hard drive has moving parts, it is much more likely to fail over time than a memory chip; if a computer fails after a few minutes of use, or makes any noise over the course of a failure, it is better to suspect the hard drive than the RAM memory as the source of the problem.