Microsoft KB Archive/156492

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GP Fault or Fatal Exception Error on Intel MMX CPU

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Q156492

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The information in this article applies to:


 * Microsoft Windows 95

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SYMPTOMS
When you are running a program or using a device driver that calls MMX- specific instructions in the retail release of Windows 95 on a system with an Intel processor supporting the MMX instruction set, the following symptoms may occur:


 * A general protection (GP) fault error message
 * A fatal exception error message on a blue screen

This problem does not occur with Windows 95 OEM Service Release 2 or later.

CAUSE
The retail release of Windows 95 does not properly support some MMX instructions if they are called from a device driver or from program code running in protection level 0 (Ring 0, also known as privileged or Kernel mode). If these instructions are issued while the processor is operating in Ring 0, a GP fault or other serious error may occur.

RESOLUTION
This issue is resolved by the following updated file for Windows 95 and OEM Service Release 2 (OSR2), and later versions of this file:

  VMCPD.VXD  version 4.10.1505  dated 5/20/97  18,606 bytes

STATUS
Microsoft has confirmed this to be a problem in Microsoft Windows 95 and OEM Service Release 2 (OSR2). An update to address this problem is now available, but is not fully regression tested and should be applied only to computers experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft does not recommend implementing this update at this time. Contact Microsoft Technical Support for additional information about the availability of this update.

This issue is resolved in Microsoft Windows 98.

MORE INFORMATION
For additional information about Windows 95 updates, please see the following article in the Microsoft Knowledge Base:

"Q161020 Implementing Windows 95 Updates" Additional query words: gpf

Keywords : kbhw win95

Issue type : kbprb

Technology : kbWin95search kbWin95