Microsoft KB Archive/74152

= EMM386.EXE Slows Down System Performance =

Article ID: 74152

Article Last Modified on 11/16/2006

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APPLIES TO


 * Microsoft MS-DOS 5.0 Standard Edition
 * Microsoft MS-DOS 5.0a
 * Microsoft MS-DOS 6.0 Standard Edition
 * Microsoft MS-DOS 6.2 Standard Edition
 * Microsoft MS-DOS 6.21 Standard Edition
 * Microsoft MS-DOS 6.22 Standard Edition

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This article was previously published under Q74152



SUMMARY
Because EMM386.EXE puts the central processing unit (CPU) in protected mode and hooks all general protection (GP) faults, a slowdown of up to 10 percent of system performance is expected behavior when running EMM386.EXE.



MORE INFORMATION
Any interrupt called that jumps to the interrupt table at the base of conventional memory when EMM386.EXE is loaded will cause a GP fault. EMM386.EXE will then hook these GP faults, determine if the interrupt is safe to call, then jump to the address pointed to by the interrupt vector that caused the GP fault. This will cause a decrease in system performance.

The performance decrease should be no more than 10 percent. If the decrease is greater, it is probably due to other factors.

For more information on general protection faults, see &quot;The 80386 Book,&quot; published by Microsoft Press.

Additional query words: 6.22 5.00 5.00a 6.00 6.20 slow gpf

Keywords: KB74152

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