System Locks While Using DOS Expanded Memory

DocumentID: 615509
Revision Date: 29-Feb-96 1:36:45 PM

The information in this document applies to:
WordPerfect® 5.1 for DOS

Problem

Symptoms: The computer locks when a user executes WordPerfect 5.1 while using the DOS expanded memory manager, EMM386.EXE. EMM386.EXE is a program that can use extended memory to simulate expanded memory. WP 5.1 can use this simulated expanded memory as if it were physical expanded memory when using the /R startup option. Even though the /R startup option was not used, WP 5.1 was conflicting with the expanded memory page frame. Note: EMM386 uses about 80K of extended memory to run. If you specify, "EMM386.EXE NOEMS," Windows 3.0 or 3.1 cannot simulate expanded memory for those programs requiring it. EMM386 can also cause EMM386 Exception Errors when hotkeying between or exiting from DOS applications in Windows 3.1. Solutions: The customer REMarked out (by placing REM at the beginning of the line) EMM386.EXE from the CONFIG.SYS file, and that solved the problem. For another customer using an IBM M-40 laptop, adding the following switch to the EMM386 driver in the CONFIG.SYS file corrected the problem. DEVICE=C:\DOS\EMM386.EXE NOMOVEXBDA X=E000-EFFF The M-40 has BIOS at E000 that is not reliably detected by the current version of MSD or Memmaker--even if the customer is not experiencing problems, using the X+E000-EFFF will save trouble later. How/Why: NOMOVEXBDA is an EMM386.EXE parameter that was undocumented prior to DOS 6.0. NOMOVEXBDA prevents EMM386 from relocating the extended BIOS data into upper memory. Every PC has a BIOS data area located in low memory that the BIOS uses as a kind of running scratchpad for the state of the system. Recorded in this data area are everything from current video mode, to what keystrokes are currently buffered waiting to be executed, to whether or not the floppy drive is currently spinning. IBM PS/2's and an increasing number of clones find the normal BIOS data area too restrictive, and so their BIOS's stake out an extended BIOS data area to give themselves more working room. Computers that report slightly less than a normal 640K of conventional memory usually have this extended BIOS Data Area. The XBDA usually takes away 1K of memory. If EMM386.EXE detects the existence of the XBDA, it will automatically relocate it into upper memory to regain that 1K of conventional memory. The information most often kept in the XBDA is mouse status information. If EMM386 relocates the XBDA to someplace in upper memory where it conflicts with something else, mouse behavior may become erratic or, usually, the computer will lock. NOTE: After adding the NOMOVEXBDA parameter, make sure the customer completes the process by reselecting/auto-selecting the mouse/pointer.

Answer:

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