Q236030: PCI Video Adapter May Not Function on Secondary PCI Bus

Article: Q236030
Product(s): Windows for Workgroups and Windows NT Networking Issues
Version(s): WINDOWS:2000; winnt:4.0
Operating System(s): 
Keyword(s): kbenv kbhw win98 multimon kbHardware
Last Modified: 10-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
- Microsoft Windows NT Workstation version 4.0 
- Microsoft Windows 98 
- Microsoft Windows 2000 Server 
- Microsoft Windows 2000 Professional 
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SYMPTOMS
========

On a computer with two PCI buses that are joined by a PCI-to-PCI bridge, a PCI
video adapter that is placed on the secondary PCI bus may not function properly.
You may experience any of the following symptoms:

- The video adapter is not recognized at the hardware level.

- Windows NT 4.0 may report parity errors while it is loading the video
  drivers.

- Video distortion may occur.

- The secondary video adapter is not detected while you are configuring
  multiple monitor support in Windows 2000 or Windows 98.

CAUSE
=====

This behavior can occur if the computer's BIOS does not correctly set the VGA
Enable and ISA Enable bits on the PCI bridges. If the BIOS does not correctly
set these bits on the PCI bridges, a resource conflict can occur between the
bridges.

RESOLUTION
==========

To resolve this issue, contact the manufacturer of the BIOS to inquire about
obtaining a BIOS revision that configures the VGA Enable bit and the ISA Enable
bit properly for the PCI bridges.

As a workaround, you may be able to install the PCI video adapter in one of the
slots on the primary PCI bus. Consult your computer documentation to determine
which PCI slots make up the primary bus on your computer.

MORE INFORMATION
================

The issue discussed in this article is a hardware problem; contact your hardware
manufacturer for additional information. The hardware manufacturer may not
support certain PCI devices beyond the PCI-to-PCI bridge.

The industry-standard PCI bus architecture limits a single bus to three PCI
slots. Additional PCI slots are on a separate PCI bus and must go through a
PCI-to-PCI bridge. On a computer that has a primary and secondary bus joined by
a PCI-to-PCI bridge, the primary bus has only two PCI slots available; one slot
is used for the PCI-to-PCI bridge. The PCI-to-PCI bridge is actually a PCI
translator that decodes and encodes address calls that are being passed upstream
from, or downstream to, the secondary PCI bus. This process is managed by the
computer's BIOS.

For additional information about configuring the PCI-to-PCI bridge, visit the
following Microsoft Web site:

  http://www.microsoft.com/hwdev/pci/vgacard.htm

For additional information about preventing PCI resource conflicts and
troubleshooting multiple monitors, click the article numbers below to view the
articles in the Microsoft Knowledge Base:

  Q148501 Preventing PCI Resource Conflicts on Intel-Based Computers

  Q170922 How PCI Devices Are Detected and Why They May Fail

  Q238886 How to Set Up and Troubleshoot Multiple Monitors in Windows 2000

Additional query words: multimon display

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Keywords          : kbenv kbhw win98 multimon kbHardware 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbwin2000Serv kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbwin2000ServSearch kbwin2000Search kbwin2000ProSearch kbwin2000Pro kbWin98search kbWin98
Version           : WINDOWS:2000; winnt:4.0
Issue type        : kbprb

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