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4-12 361834-002 Technical Reference Guide
System Support
8259 Mode
The 8259 mode handles interrupts IRQ0-IRQ15 in the legacy (AT-system) method using
8259-equivalent logic. Table 4-7 lists the standard source configuration for maskable interrupts
and their priorities in 8259 mode. If more than one interrupt is pending, the highest priority
(lowest number) is processed first.
Table 4-7.
Maskable Interrupt Priorities and Assignments
Priority Signal Label Source (Typical)
1 IRQ0 Interval timer 1, counter 0
2 IRQ1 Keyboard
3 IRQ8- Real-time clock
4 IRQ9 Unused
5 IRQ10 PCI devices/slots
6 IRQ11 Audio codec
7 IRQ12 Mouse
8 IRQ13 Coprocessor (math)
9 IRQ14 Primary IDE controller
10 IRQ15 Sec. IDE I/F controller (not available on SATA units)
11 IRQ3 Serial port (COM2)
12 IRQ4 Serial port (COM1)
13 IRQ5 Network interface controller
14 IRQ6 Diskette drive controller
15 IRQ7 Parallel port (LPT1)
-- IRQ2 NOT AVAILABLE (Cascade from interrupt controller 2)