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Adding Expansion Cards
6/4 APRICOT 340 OWNER’S HANDBOOK
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)
Audio in MS/LS models
IRQ13 Coprocessor
IRQ6 Diskette controller IRQ14 Primary ATA/IDE interface
IRQ7 Parallel port (default) IRQ15 Secondary ATA/IDE interface