A d d i n g E x p a n s i o n C a r d s

Interrupt request level (IRQ)

The interrupt request level or IRQ (the two terms are used interchangeably) is the line over which the expansion card sends a signal to get the attention of, or interrupt, the processor.

Your computer has interrupt levels numbered IRQ0 to IRQ15. Most of these are reserved for components on the computer’s motherboard. Some of these interrupts are fixed; others can be re- assigned, or freed by disabling the component with BIOS Setup.

The following table lists the interrupts used by the computer. Interrupts that have no default assignment can be used by expansion cards.

IRQ3 is available if you disable serial port B with the BIOS Setup utility. Similarly, IRQ4 is available if you disable serial port A. Obviously, you shouldn’t disable either one unless you have no intention of using the affected port.

The MS/LS audio system can be assigned an interrupt other than IRQ 5 if necessary, by means of its Windows device driver.

If you configure the parallel port to Standard mode, its interrupt (IRQ7 or IRQ 5) can usually be used by an expansion card without affecting the operation of the port. This may not be possible if you use the port in an Extended mode.

IRQ

Default assignment

IRQ

Default assignment

IRQ0

System

IRQ8

Real time clock

IRQ1

Keyboard controller

IRQ9

-

IRQ2

Slave interrupt controller

IRQ10

-

IRQ3

Serial port B

IRQ11

-

IRQ4

Serial port A

IRQ12

Mouse

IRQ5

Parallel port (alternative)

IRQ13

Coprocessor

 

Audio in MS/LS models

 

 

IRQ6

Diskette controller

IRQ14

Primary ATA/IDE interface

IRQ7

Parallel port (default)

IRQ15

Secondary ATA/IDE interface

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