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
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
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
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.
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