7.3 Interrupt Request (IRQ) Lines
Table 39
IRQ Lines in PIC mode
IRQ#
Available
Typical Interrupt Source
Connected to Pin
0
No
Counter 0
N.A.
1
No
Keyboard
N.A.
2
No
Cascade Interrupt from Slave PIC
N.A.
3
Note 1
Serial Port 2 (COM2) / Generic
IRQ3 via SERIRQ
4
Note 1
Serial Port 1 (COM1) / Generic
IRQ4 via SERIRQ
5
Yes
N.A.
IRQ5 via SERIRQ
6
Note 1
Floppy Drive Controller / Generic
IRQ6 via SERIRQ
7
Note 1
Parallel Port 1 (LPT1) / Generic
IRQ7 via SERIRQ
8
No
Real-time Clock
N.A.
9
Note 2
SCI / Generic
IRQ9 via SERIRQ
10
Yes
N.A.
IRQ10 via SERIRQ
11
Yes
N.A.
IRQ11 via SERIRQ
12
Note 1
PS/2 Mouse / Generic
IRQ12 via SERIRQ
13
No
Math processor
N.A.
14
Note 1
IDE Controller 0 (IDE0)
IRQ14
15
No
N.A.
N.A.
In PIC mode, the PCI bus interrupt lines can be routed to any free IRQ.
Notes
1. Default, but can be changed to another interrupt.
2. In ACPI mode, IRQ9 is used for the SCI (System Control Interrupt). The SCI can be
shared with a PCI interrupt line.
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