Technical Reference Guide
8259 Mode
The 8259 mode handles interrupts IRQ0-IRQ15 in the legacy (AT-system) method using 8259-
equivalent logic. Table 4-6 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 4-6.
Maskable Interrupt Priorities and Assignments
Table 4-6.
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
I
RQ15
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)
Int. Cntlr.
APIC Mode
The Advanced Programmable Interrupt Controller (APIC) mode provides enhanced interrupt
rocessing with the following advantages:
p
pt acknowledge cycle by using a separate (APIC) bus
♦
Eliminates the processor’s interru
♦
Programmable interrupt priority
Additional interrupts (total of 24)
♦
The APIC mode accommodates eight PCI interrupt signals (INTA-..INTH-) for use by PCI
evices. The PCI interrupts are evenly distributed to minimize latency and wired as follows:
d
82801
PCI
Slot 1
PCI
Slot 2
PCI
Slot 3
PCI
Slot 4
PCI
Slot 5
AGP
Slot
NIC
I/F [1]
I/F #2
USB
INTA-
IN
TA-
TD-
— — —
INTB-
—
—
—
—
— — — —
INTC-
TB-
—
—
INTD-
—
—
—
—
— IN
TB-
— —
INTE-
—
—
—
—
— — IN
TA-
—
INTF-
INTC-
INTB-
INTA-
INTD-
INTB-
— — —
INTG-
IN
TD-
TC-
— — —
INTD-
INTC-
INTB-
IN
ired
IN
INTA-
INTD-
INTC-
INTA- INTA-
INTC-
INTB-
INTA-
IN
INTH-
—
—
—
—
— — —
INTC-
NOTES:
H. Will be reported by BIOS as using INTA but is NOT shared with
nly.
ST, DT, MT, CMT form factors only.
W
to
[1] Connection internal to the IC
other functions using INTA.
ST, SFF, DT. MT, CMT form factors o
hp compaq d330 and d530 Series of Personal Computers
Featuring the Intel Pentium 4 Processor
First Edition - June 2003
4-15