System Overview
1-15
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IRQ0
Generated by system timer.
IRQ1
Generated by I/O controller to indicate full keyboard output
buffer.
IRQ2
Generated internally by interrupt controller to enable IRQ8
through IRQ15.
IRQ3
1
Available for use by an expansion card.
IRQ4
Generated by I/O controller to indicate that the device connected
to the serial port requires service (COM1 or COM3).
IRQ5
Default audio IRQ assignment.
IRQ6
Generated by I/O controller to indicate that the diskette drive or
tape drive requires service.
IRQ7
Generated by I/O controller to indicate that the device connected
to the parallel port requires service.
IRQ8
Generated by I/O controller for each tick of the RTC.
IRQ9
2
Available for use by an expansion card.
IRQ10
Available for use by an expansion card.
IRQ11
3
Default PCI IRQ assignment.
IRQ12
Generated by I/O controller to indicate full mouse-output buffer.
IRQ13
Generated by math coprocessor to indicate a coprocessor error.
IRQ14
Generated by a device connected to the primary EIDE interface
to indicate that the device requires service.
IRQ15
Generated by a device connected to the secondary EIDE inter-
face to indicate that the device requires service. If no device is
connected to the secondary EIDE interface, IRQ15 is available for
use by an expansion card.
1
IRQ3 is available provided that no other device in the computer (such as a modem) is
using COM2 or COM4.
2
IRQ9 is available to PCI expansion cards only.
3
The PCI IRQ line is assigned to an available IRQ line after all ISA expansion cards have
been configured. If an ISA expansion card is configured for IRQ11, the PCI IRQ is as-
signed to another available IRQ line.
