How to Use Windows Memory Diagnostics

Memory problems are one of the most common types of hardware problem. Memory problems can prevent Windows from starting and cause unpredictable Stop errors when Windows has started. Because memory-related problems can cause intermittent failures, they can be difficult to identify.

Fortunately, Windows includes Windows Memory Diagnostics, an offline diagnostic tool that automatically tests your computer's memory. Windows Memory Diagnostics tests your computer's memory by repeatedly writing values to memory and then reading those values from memory to verify that they have not changed. To identify the widest range of memory failures, Windows Memory Diagnostics includes three different testing levels:

• Basic Basic tests include:
  • MATS+
  • INVC
  • SCHCKR (which enables the cache)
• Standard All basic tests, plus:
  • LRAND
  • Stride6 (which enables the cache)
  • CHCKR3
  • WMATS+
  • WINVC
• Extended All standard tests, plus:
  • MATS+ (which disables the cache)
  • Stride38
  • WSCHCKR
  • WStride-6
  • CHKCKR4
  • WCHCKR3
  • ERAND
  • Stride6 (which disables the cache)
  • CHCKR8

Although the specifics of each of these tests are not important for administrators to understand, it is important to understand that memory testing is never perfect. Failures are often intermittent and may occur only once every several days or weeks in regular usage. Automated tests such as those done by Windows Memory Diagnostics increase the likelihood that a failure can be detected; however, you can still have faulty memory while Windows Memory Diagnostics indicates that no problems were detected. To minimize this risk, run the Extended tests and increase the number of repetitions. The more tests you run, the more confident you can be in the result. If you have even a single failure, it indicates faulty memory.

After Windows Memory Diagnostics completes testing, the computer will automatically restart. Windows will display a notification bubble with the test resultsc and you can view events in the System Event Log with the source MemoryDiagnosticsResults (Event ID 1201).

If you do identify a memory failure, it is typically not worthwhile to attempt to repair the memory. Instead, you should replace unreliable memory. If the computer has multiple memory cards and you are unsure which card is causing the problem, replace each card and then rerun Windows Memory Diagnostics until the computer is reliable.

If problems persist even after replacing the memory, the problem is caused by an outside source. For example, high temperatures (often found in mobile PCs) can cause memory to be unreliable. Although computer manufacturers typically choose memory specifically designed to withstand high temperatures, adding third-party memory that does not meet the same specifications can cause failure. Besides heat, other devices inside the computer can cause electrical interference. Finally, motherboard or processor problems may occasionally cause memory communication errors that resemble failing memory.