4-12 www.hp.com 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
2IRQ1Keyboard
3IRQ8-Real-time clock
4IRQ9Unused
5 IRQ10 PCI devices/slots
6IRQ11Audio codec
7IRQ12Mouse
8 IRQ13 Coprocessor (math)
9 IRQ14 Primary IDE controller
10 IRQ15 Sec. IDE I/F controller (not available on SATA units)
11 I R Q 3 S e r i a l p o r t ( C O M 2 )
12 I RQ4 Serial po r t ( COM 1)
13 IRQ5 Network interface controller
14 IRQ6 Diskette drive controller
15 IRQ7 Parallel port (LPT1)
-- IRQ2 NOT AVAILABLE (Cascade from interrupt controller 2)
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