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Article ID: 134503 - Last Review: January 19, 2007 - Revision: 2.4

This article was previously published under Q134503

SYMPTOMS

When you are running Windows 95, you may receive frequent (every 10 or 20 minutes) "Parity Error" messages on a blue screen. When you receive such a message, you must restart the computer.

CAUSE

Parity errors are usually caused by defective memory chips in the computer. For more information about parity errors, please see the following article in the Microsoft Knowledge Base:
93521  (http://support.microsoft.com/kb/93521/EN-US/ ) Parity Errors in Windows 3.x
Parity errors can also be caused by:
  • Mismatched RAM. That is, mixing different types of SIMMs (such as parity and non-parity RAM) on the motherboard.
  • Incorrect RAM for the motherboard. For example, non-parity RAM on a motherboard requiring parity RAM.
  • Non-proprietary RAM on a motherboard that required proprietary RAM.

RESOLUTION

There are two methods you can use to identify whether defective memory chips are causing the problem:
  • Remove or replace memory chips in the computer to see if the problem is resolved.
  • Try limiting the amount of memory that Windows 95 uses. To do so, follow these steps:

    1. Use any text editor (such as Notepad) to edit the System.ini file.
    2. Add the following line in the [386Enh] section of the file
      MaxPhysPage=<nnn>
      where <nnn> determines the amount of memory you want Windows 95 to use.

      To limit Windows 95 to the first 16 MB of memory, add the following line:
      MaxPhysPage=FFF
      To limit Windows 95 to the first 8 MB of memory, add the following line:
      MaxPhysPage=7FF
      To limit Windows 95 to the first 4 MB of memory, add the following line:
      MaxPhysPage=3FF
    3. Save and then close the System.ini file.
    4. Restart your computer.
For additional information, click the following article numbers to view the articles in the Microsoft Knowledge Base:
142546  (http://support.microsoft.com/kb/142546/EN-US/ ) How to Use a RAM Drive to Troubleshoot Memory
138788  (http://support.microsoft.com/kb/138788/EN-US/ ) Bad RAM Causes Fatal Exception Errors Running Windows 95/98

MORE INFORMATION

Defective memory chips may not be detected by memory checking tools. Some memory checking programs are not adequate tests because they do not test RAM in the same way that Windows uses RAM. Most memory checkers use read/write cycles when scanning memory. Since Windows is executing code from memory, it uses execute cycles. Execute cycles are different from read/write cycles and are more vulnerable to parity errors. It is possible for memory checking programs to find parity errors if the memory is extremely faulty. Bad memory chips can also cause the following situations:

  • Fatal Exception errors
  • Himem.sys load failures in normal or Safe mode
  • Random lockups
  • The computer may stop responding (hang) as soon as you turn it on

APPLIES TO
  • Microsoft Windows 95
  • Microsoft Windows 98 Standard Edition
  • Microsoft Windows 98 Second Edition
  • Microsoft Windows Millennium Edition
Keywords: 
kbenv kberrmsg kbfaq kbhardware KB134503
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