by January 4, 1998 0 comments

Your PC has been working
fine for some time now. And you decide to add something
new–a CD-ROM driver or a sound card or maybe a new
display card. And suddenly your machine starts
misbehaving. What went wrong when you added a new card?
Surely you fixed the card properly and installed all the
drivers supplied with the card. Time for a panic call to
the vendor? Will they be able to help? Before reaching
for the telephone, here are a few things that you can do

A majority of these
problems are caused by IRQ conflicts. PCI cards and Win
95 were supposed to make IRQ conflicts a thing of the
past. Unfortunately, not all your installed cards are
PCI, and even with PCI, we have come across rare
instances of clashes that had to be resolved manually.

The basic rule is that no
two devices can have the same IRQ. Some system devices
are provided with pre-defined IRQs. For example, COM
ports take IRQ 3 and 4, parallel port 7, disk controller
14 and 15, and sound card normally takes IRQ 5. But you
can change that. Other devices like Network and SCSI
cards for your scanner, or CD-Writer might prompt you for
manual configuration.

In case of ISA devices you
have to set the IRQ manually. PCI devices are
automatically set to available IRQ numbers by the BIOS
itself. Setting PCI configuration to Auto mode in the
BIOS will generally do this. If for any reason PCI
devices clash with automatic IRQ settings, you have to
change these settings manually. But before that you have
to take care about what you are actually changing.

In Win 95, you can easily
configure and clear IRQ conflicts from System Properties
control panel. From the Start button, select
Settings/Control Panel/System. Select Device Manager.
This tab lists all devices connected to your system.

If you have selected the
View devices by type option, you will see a list of
device types like hard drive, display adapter, floppy
disk controllers, etc, listed in alphabetic order.
Clicking on the + sign in the box on the left of any of
these items, displays a list of installed devices of that
type. For example, clicking on the + sign next to the
display adapters shows the installed display adapters
(normally there should be only one display adapter). Go
to the device that is not functioning and click on the +
sign to see what are the installed devices.

An item that is installed
but not present or not working is identified with a black
exclamation mark in a yellow circle. Select this item and
click on the Properties button at the bottom of the
System Properties window. The Resources tab lists the IRQ
being used. In order to change the IRQ, you need to first
put off the Use AutomaticSettings option and then click
on Change Setting after selecting the resource
whose value you want to change. Note that all devices may
not have resource allocations, and that all devices with
resource allocations may not allow you to change them
from here (you may need to set the BIOS first).

A more common occurrence
is that devices that are no longer installed on the
system still show up, or multiple instances of the same
device may be installed. In either case, the offending
instances can be deleted by selecting them and clicking
on Remove in the System Properties window.

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