IRQ Numbers
IRQ 0
System timer
This is reserved for
the internal system timer. This is not available to
peripherals or other devices.
IRQ 1
Keyboard
Reserved for the
keyboard controller. This interrupt is exclusively for
keyboard input.
IRQ 2
Cascade interrupt for
IRQs 8-15
This interrupt cascades
the second interrupt controller to the first.
IRQ 3
Second serial port
(COM2)
The interrupt for the
second serial port and often the default interrupt for the
fourth serial port (COM4).
IRQ 4
First serial port
(COM1)
This interrupt is
normally used for the first serial port. On devices that do
not use a
PS/2 mouse, this
interrupt is almost always used by the serial mouse. This is
also the default interrupt for the third serial port (COM3).
IRQ 5
Sound card
This interrupt is the
first choice that most sound cards make when looking for an
IRQ setting.
IRQ 6
Floppy disk controller
This interrupt is
reserved for the floppy disk controller.
IRQ 7
First parallel port
This interrupt is
normally reserved for the use of the printer. If a printer
is not being used, this interrupt can be used for other
devices that use parallel ports.
IRQ 8
Real-time clock
This interrupt is
reserved for the system's real-time clock timer and can not
be used for any other purpose.
IRQ 9
Open interrupt
This interrupt is
typically left open on devices for the use of peripherals.
IRQ 10
Open interrupt
This interrupt is
typically left open on devices for the use of peripherals.
IRQ 11
Open interrupt
This interrupt is
typically left open on devices for the use of peripherals.
IRQ 12
PS/2 mouse
This interrupt is
reserved for the PS/2 mouse on machines that use one. If a
PS/2 mouse is not used, the interrupt can be used for other
peripherals, such as network card.
IRQ 13
Floating point
unit/coprocessor
This interrupt is
reserved for the integrated floating point unit. It is never
available to peripherals or other devices as it is used
exclusively for internal signaling.
IRQ 14
Primary IDE channel
This interrupt is
reserved for use by the primary IDE controller. On systems
that do not use IDE devices, the IRQ can be used for another
purpose.
IRQ 15
Secondary IDE channel
This interrupt is
reserved for use by the secondary IDE controller.
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