CompTIA A+ Training Kit: Understanding RAM and CPUs

  • 12/15/2012


You might occasionally run across a system that is having a problem with the CPU or RAM. Sometimes the problems are consistent, but more often they are intermittent; sometimes you’ll see the problem, sometimes you won’t.

Intermittent problems are frequently related to overheating, so a good first step is to ensure that the system has adequate airflow. Shut the system down, open the case, and either vacuum it with an ESD-safe vacuum or take it outside and blow it out with compressed air.

Common Symptoms

The following are some common symptoms and possible causes related to the CPU or RAM:

  • Unexpected shutdowns. If the system is randomly shutting down or rebooting, the most likely cause is a heat problem. Check the ventilation and clean out the fans.

  • System lockups. When a computer stops responding to inputs from the keyboard or mouse, technicians refer to it as frozen or locked up. This can also be due to heat issues. Check the ventilation.

  • Continuous reboots. In some cases, a hardware issue can prevent the system from booting completely. It starts, gets so far, and then resets itself. This is more common after a faulty software update, but it can be due to a hardware problem. If you’ve just replaced hardware, double-check your steps. If that isn’t the issue, boot into Safe Mode and troubleshoot the operating system using the steps provided in Chapter 17, “Troubleshooting Windows Operating Systems.”


If you’ve cleaned out the system and you’re still having intermittent problems, there are two primary things to check:

  • Power supply. An overloaded or failing power supply can cause intermittent problems. Use a multimeter to verify the voltages. If the voltages are out of tolerance, replace the power supply.

  • RAM. It is possible to have a certain area of RAM that is faulty. The system can work until it writes data to that area, and then it shuts down or freezes. In some cases, you receive a stop error or blue screen of death (BSOD) with an error code indicating a memory problem. If you suspect a RAM problem, use a memory checker to run memory diagnostics.

Windows Memory Diagnostics

Windows Vista and Windows 7 include the Windows Memory Diagnostic tool, and steps later in this section show how to run it. It’s easy to run and can perform in-depth testing of the system RAM and the cache within the CPU.

The diagnostics include three sets of tests (basic, standard, and extended). By default, it runs two passes of the standard set of tests, and this is usually good enough. If this passes but you still suspect you have memory problems, you can choose other options by pressing F1 to modify them. For example, if you have an intermittent problem and want to do detailed tests for a day or longer, you can set the pass count to 0 and it will run continuously.

You can use the following steps on a Windows 7 system to run the Windows Memory Diagnostics tool:

  1. Click Start and type Memory in the Search Programs And Files text box.

  2. Select Windows Memory Diagnostic.

  3. Select Restart Now and check for problems. After the system reboots, the tests will start and you’ll see a display similar to the following graphic. If any errors are identified, they will be displayed in the Status area, but they usually won’t stop the diagnostic from running. After the test completes, the system automatically reboots.

  4. About a minute or so after you log on, you’ll see a balloon message appear in the system tray at the bottom right indicating the results. It appears and then fades out. If you miss it, you can also view the results in the System log via the Event Viewer. It’s listed with a source of MemoryDiagnostics-Results and an Event ID of 1201.

If you’re unable to boot into the operating system, you can access the Windows Memory Diagnostic by using several other methods. Each of the following methods will start the Windows Recovery Environment (Windows RE), showing the System Recovery Options, as shown in Figure 3-13. You can then select Windows Memory Diagnostic.

  • Press F8 as the system is booting to access the Advanced Boot Options page and select Repair Your Computer.

  • Start from a Windows Vista installation DVD, select the Language, and then click Repair Your Computer.

  • Create a system repair disc and use it to boot directly into the Windows RE.

Figure 3-13

Figure 3-13. Running Windows Memory Diagnostic from boot DVD.

If the memory diagnostic gives any errors, you might be able to do a quick fix by reseating the memory sticks. Power your system down and open it up. Hook up an ESD strap to ground yourself with the system and then locate the RAM. Press the tabs on each side to pop out each DIMM, and then push each back into the slot until the tabs lock. This same fix can also be used on any expansion card.

You might be wondering why this works. Electrical components expand and contract from heat and cold, causing some movement. Additionally, the electrical contacts can become tarnished, preventing a good connection. When you pop it out and push it back, the friction scrapes the tarnish off the contacts. With the tarnish removed, it has a good connection.


CPU-Z is a handy freeware utility that you can use to view some detailed information on your system. It’s been around a long time and has helped many technicians. A copy is on the CD, and you can find a link about the installation here:

Figure 3-14 shows a screen shot of the CPU tab of the CPU-Z application. You can see that this provides some detailed information about the processor, clocks, and cache.

Figure 3-14

Figure 3-14. CPU-Z.

If you click the Mainboard tab, it gives you details about your motherboard and BIOS. The Memory tab provides overall information about installed memory, and the SPD tab enables you to select individual memory slots to determine what is installed. As you’d expect, the Graphics tab provides details about the graphics card. The About tab includes buttons you can use to save the details of the report as either a text file or an HTML file.