Microsoft KB Archive/70807

PRWIN9103015: DPMI Switch Crashes VM If No EMS Pages Free ID Number: Q70807

3.00 WINDOWS buglist3.00 fixlist3.10

Summary:

PROBLEM ID: WIN9103015

SYMPTOMS In enhanced mode Windows 3.0, using the MS-DOS Protected Mode Interface (DPMI) switch to protected mode may crash the current virtual machine (VM).

CAUSE There are no pages on the expanded memory specification (EMS) free page list.

RESOLUTION Microsoft has confirmed this to be a problem in Windows version 3.0. This problem can be avoided by following these seven steps:


 * 1) Allocate an EMS handle.
 * 2) Touch four memory pages.
 * 3) Enter the Win386 critical section.
 * 4) Touch the same memory pages again.
 * 5) Free the EMS handle.
 * 6) Switch to protected mode using DPMI.
 * 7) Leave the Win386 critical section.

This problem was corrected in Windows version 3.1.

Additional reference words: 3.00