KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q125389: How to Simulate INT 15 Rather Than Calling EISA BIOS Directly

Article: Q125389
Product(s): Microsoft Windows 95.x Retail Product
Version(s): 95
Operating System(s): 
Keyword(s): win95
Last Modified: 17-DEC-2000

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows 95 
-------------------------------------------------------------------------------

IMPORTANT: This article contains information about editing the registry.
Before you edit the registry, you should first make a backup copy of the
registry files (System.dat and User.dat). Both are hidden files in the
Windows folder.

SYMPTOMS
========

You computer stops responding (hangs) during the boot process.

CAUSE
=====

Some programs (such as QEMM Stealth and EMM386.EXE with the /HIGHSCAN switch)
map over part of the BIOS. If RAM has been mapped over the EISA BIOS, your
computer may hang when Windows calls the BIOS.

Windows 95 calls an EISA BIOS in one of two ways:

- Using INT 15.

- With a direct call to a published entry point.

By default, Windows calls the BIOS directly rather than by using INT 15.

RESOLUTION
==========

Windows 95 attempts to detect cases of RAM mapping so that it can change the way
it calls the EISA BIOS. For example, if Windows 95 detects QEMM Stealth it calls
the BIOS by simulating INT 15. To do this, Windows adds an EISASimulateInt15
entry to the registry and gives the entry a value of

1. The default value, 00, means that Windows communicates with the EISA

BIOS directly.

If you suspect that your computer is hanging because of the way Windows is
accessing the BIOS, add EISASimulateInt15 to

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\System

in the registry and give it a value of 00 or 01. A value of 00 causes Windows to
call the BIOS directly, and a value of 01 causes Windows to simulate INT 15 to
call the BIOS.

NOTE: For information about how to edit the registry, view the Changing Keys And
Values online Help topic in Registry Editor (Regedit.exe). Note that you should
make a backup copy of the registry files (System.dat and User.dat) before you
edit the registry.

WARNING: Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall Windows 95. Microsoft cannot guarantee that problems
resulting from the incorrect use of Registry Editor can be solved. Use Registry
Editor at your own risk.

Additional query words: eisa enumerator

======================================================================
Keywords          : win95 
Technology        : kbWin95search kbZNotKeyword3
Version           : 95

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.