PC Hardware A Beginner’s Guide

(^288) PC Hardware: A Beginner’s Guide

Configuring IRQ Settings

There is a variety of ways to set an IRQ setting for a particular adapter or controller ex-

pansion cards. Most of today’s expansion cards are PCI (Peripheral Component Intercon-

nect) and are Plug-and-Play compatible (more on this later in this section). However, ISA

(Industry Standard Architecture), EISA (Extended ISA), and VESA (Video Electronics

Standards Association) local bus cards are still supported on most PC motherboards, and

these cards require different amounts of physical setup to assign their IRQ (and other sys-

tem resource settings).

Regardless of the method used to set the IRQ for a new device, the current IRQ set-

tings should be reviewed before the new card is installed and configured. You should

also review the documentation of the new device to determine the IRQ (and system re-

source) settings it wishes to use. If the default IRQ of the device is available on the system,

there should not be any problems with the installation and operation of the device. How-

ever, if it is not available, you may need to reassign the IRQ or to reconfigure the new de-

vice to an available IRQ.

IRQ Slot Size (bits) PC XT Bus PC AT Bus Current (Pentium-class PCs)

6 8-bit Floppy disk

controller

(FDC)

FDC FDC

7 8-bit LPT1 LPT1 LPT1

8 n/a Real-time clock

(RTC)

RTC RTC

9 8-bit n/a Available Available

10 16-bit n/a Available Available

11 16-bit n/a Available Available

12 16-bit n/a PS/2

mouse

PS/2 mouse

13 n/a n/a Math

coprocessor

Math coprocessor

14 16-bit n/a HDC Primary IDE controller

15 16-bit n/a Available Secondary IDE controller

Table 13-2. IRQ Assignments on Bus Structures(continued)