CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [99]
Access to RAM usually requires removing a panel or lifting up the keyboard—the procedure varies among laptop manufacturers. Figure 6-32 shows a typical laptop RAM
Figure 6-32 A RAM access panel on a laptop
Figure 6-33 Snapping in an SO-DIMM
Before doing any work on a laptop, turn the system off, disconnect it from the AC wall socket, and remove all batteries. Use an anti-static wrist strap because laptops are far more susceptible to ESD than desktop PCs.
Practical Application
Troubleshooting RAM
“Memory” errors show up in a variety of ways on modern systems, including parity errors, ECC error messages, system lockups, page faults, and other error screens in Windows. These errors can indicate bad RAM, but often point to something completely unrelated to RAM. This is especially true with intermittent problems. The challenge for techs is to recognize these errors and then determine which part of the system caused the memory error.
You can get two radically different types of parity errors: real and phantom. Real parity errors are simply errors that the MCC detects from the parity or ECC chips (if you have them). The operating system then reports the problem in an error message, such as “Parity error at xxxx:xxxxxxxx,” where xxxx:xxxxxxxx is a hexadecimal value (a string of numbers and letters, such as A5F2:004EEAB9). If you get an error like this, write down the value (Figure 6-34). A real parity/ECC error shows up at the same place in memory each time and almost always indicates that you have a bad RAM stick.
Figure 6-34 Windows error message
Phantom parity errors show up on systems that don’t have parity or ECC memory. If Windows generates parity errors with different addresses, you most likely do not have a problem with RAM. These phantom errors can occur for a variety of reasons, including software problems, heat or dust, solar flares, fluctuations in the Force…you get the idea.
System lockups and page faults (they often go hand in hand) in Windows can indicate a problem with RAM. A system lockup is when the computer stops functioning. A page fault is a milder error that can be caused by memory issues, but not necessarily system RAM problems. Certainly page faults look like RAM issues because Windows generates frightening error messages filled with long strings of hexadecimal digits, such as “KRNL386 caused a page fault at 03F2:25A003BC.” Just because the error message contains a memory address, however, does not mean that you have a problem with your RAM. Write down the address. If it repeats in later error messages, you probably have a bad RAM stick. If Windows displays different memory locations, you need to look elsewhere for the culprit.
Every once in a while, something potentially catastrophic happens within the PC, some little electron hits the big red panic button, and the operating system has to shut down certain functions running before it can save data. This panic button inside the PC is called a non-maskable interrupt (NMI), more simply defined as an interruption the CPU cannot ignore. An NMI manifests to the user as what techs lovingly call the Blue Screen of Death (BSoD)—a bright blue screen with a scary-sounding error message on it (Figure 6-35).
Figure 6-35 Blue Screen of Death
Bad RAM sometimes triggers an NMI, although often the culprit lies with buggy programming or clashing code. The BSoD varies according to the operating system, and it would require a much lengthier tome than this one to cover all the variations. Suffice it to say that RAM could be the problem when that delightful blue screen appears.
Finally, intermittent memory errors can come from a variety of sources, including a dying power supply,