Chapter 24: Troubleshooting PC Hardware^635
checking code (ECC) memory, or SDRAM in a PC that supports only EDO
(Extended Data Output) memory will definitely cause the boot sequence to
halt. See Chapter 7 for more information on memory types.
The memory count displayed by the POST is wrong If the memory count
displayed by the POST is less than it should be, the BIOS isn’t recognizing all of
the installed memory. A wrong memory type being installed is a common cause
for this error, as well as memory banks not being completed. Another problem is
incompatible memory or more memory than the system is able to address.
The PC displays a memory error message, such as:
Memory mismatch error
Memory parity interrupt at nnnnn
Memory address error at nnnnn
Memory failure at nnnnn, read nnnnn, expecting nnnnn
Memory verify error at nnnnn, where nnnnn is the physical address in
RAM of the memory fault.
These errors typically point out problems between old memory and new memory
or a failing memory module. If removing a newly installed memory module
eliminates the error, replace the old memory with the new memory. If the error
shows u pagain, the new memory is either defective or not com patible with the
system. Another cause for these messages can be a motherboard problem.
ESD damage Intermittent memory problems—those that show up
sporadically as an error message, system crash, or a spontaneous system
reboot— have a number of possible causes, but one of the leading suspects
should be ESD (electrostatic discharge). If you are not properly grounded with
effective ESD protection when working inside the system unit, you can cause
enough damage to either completely fry a component or to create intermittent
problems that result from the circuit slowly degrading over time. Other problems
for intermittent memory problems are overheating, corrosion, or a faulty
power supply. Software-related memory problems The problems under this category
include registry errors, general-protection and page faults, and exception
errors. Registry errors happen when the Windows operating system writes
parts of the registry to a defective portion of RAM. Software bugs cause faults
and exception errors. For example, an application may release its memory
when completed or it may try to occupy the same memory address as another.
Rebooting the PC usually solves these problems.