Filter
Top Products
Technical Reference Guide
he 8259 mode handles interrupts IRQ0-IRQ15 in the legacy (AT-system) method using 8259-
quivalent logic. Table 4-8 lists the standard source configuration for maskable interrupts and
t i
r)
able 4-8. Maskable Interrupt Priorities and Assignments
Table 4-8.
8259 Mode
T
e
orities in 8259 mode. If more than one interrupt is pending, the highest priority (lowest heir pr
numbe is processed first.
T
Maskable Interrupt Priorities and Assignments
Priority Signal Label Source (Typical)
1 IRQ0 Interval timer 1, counter 0
3 IRQ8- Real-time clock
2 IRQ1 Keyboard
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 Secondary IDE I/F controller
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)
) bus
rrupt priority
s (total of 24)
evices. The PCI interrupts are evenly distributed to minimize latency and wired as follows:
Int. Cntlr.
Slot 1
Slot 2
APIC Mode
The Advanced Programmable Interrupt Controller (APIC) mode provides enhanced interrupt
processing with the following advantages:
Eliminates the processor’s interrupt acknowledge cycle by using a separate (APIC♦
♦ Programmable inte
Additional interrupt♦
he APIC mode accommodates eight PCI interrupt signals (INTA-..INTH-) for use by PCI T
d
ICH2
PCI
PCI
PCI PCI PCI
Slot 3
Slot 4 Slot 5
AGP
Slot
NIC
I/F [1]
USB
I/F #2
INTA- INTA- INTD- INTC- INTB- INTD- -- -- --
INTB- --
-- -- -- -- -- -- --
INTC- INTB- INTA- INTD- INTC- INTA- INTA- -- --
INTD- -- -- -- -- -- INTB- -- --
INTE- -- -- -- -- --- -- INTA- --
INTF- INTC- INTB- INTA- INTD- INTB- -- -- --
INTG- INTD- INTC- INTB- INTA- INTC- -- -- --
INTH- -- -- -- -- -- -- -- INTC-
NOTES:
[1] Connection internal to the ICH2. Will be reported by BIOS as using INTA but is NOT shared with
other functions using INTA.
Desktop and configurable minitower systems only.
Configurable minitower systems only.
Wired
to
Compaq Evo and Workstation Personal Computers
Featuring the Intel Pentium 4 Processor
Second Edition - January 2003
4-17