EMM386.EXE Slows Down System Performance (74152)



The information in this article applies to:
    Microsoft MS-DOS operating system 5.0
    Microsoft MS-DOS operating system 5.0a
    Microsoft MS-DOS operating system 6.0
    Microsoft MS-DOS operating system 6.2
    Microsoft MS-DOS operating system 6.21
    Microsoft MS-DOS operating system 6.22

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 "The 80386 Book," published by Microsoft Press.

Modification Type: Major Last Reviewed: 5/12/2003
Keywords: KB74152