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Q129955: IRQ Conflicts with PCI Display Adapters

Article: Q129955
Product(s): Microsoft Windows 95.x Retail Product
Version(s): 95
Operating System(s): 
Keyword(s): win95
Last Modified: 17-DEC-2000

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The information in this article applies to:

- Microsoft Windows 95 
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SYMPTOMS
========

When you install a Peripheral Component Interconnect (PCI) video adapter that is
configured to use a particular interrupt (IRQ), Windows 95 may configure it to
use another IRQ that is already in use by another device.

CAUSE
=====

PCI devices can share PCI IRQs, but Windows 95 does not support sharing PCI IRQs
with other non-PCI devices (such as an IDE controller).

Windows 95 display drivers do not use an IRQ. However, PCI adapters request an
IRQ for full backward compatibility.

RESOLUTION
==========

Use Device Manager to resolve the conflict by assigning a different IRQ to one
of the conflicting devices.

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

This behavior is common to all PCI display adapters, but does not apply to
Industry Standard Architecture (ISA) or VESA Local Bus (VLB) display adapters.

PCI devices can share IRQs. This behavior is in the PCI specification and Windows
95 supports it. PCI devices must be configured by the computer's BIOS. This
occurs during the computer's Power-On Self Test (POST) before the operating
system is loaded. Windows 95 does not configure PCI devices, but uses what the
BIOS reports.

In order to get full Plug and Play functionality, Windows 95 enables inactive
devices when it starts. For example, if a second IDE controller is disabled in
the BIOS but not in Device Manager, the controller is enabled and resources are
assigned to it. To prevent this behavior, disable the inactive device and remove
it from the current configuration in Device Manager.

Note that if you are using an early version of the Micron BIOS, you should
contact Micron for a later version. Early versions of the Micron BIOS do not
configure PCI cards correctly, leading to conflicts with the video device on IRQ
15 or other non-valid IRQs. To correct this problem, Micron recommends that you
upgrade the ROM BIOS to revision 19. You can obtain the ROM BIOS flash upgrade
from Micron, or from Micron's Web site at:

  http://www.mei.micron.com

Download the 90_PM_19.ZIP file from Micron's Web site.

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Keywords          : win95 
Technology        : kbWin95search kbZNotKeyword3
Version           : 95

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