307013-003 Datasheet, PDF (140/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
5.10
Advanced Programmable Interrupt Controller
(APIC) (D31:F0)
In addition to the standard ISA-compatible PIC described in the previous chapter, the
ICH7 incorporates the APIC. While the standard interrupt controller is intended for use
in a uni-processor system, APIC can be used in either a uni-processor or multi-
processor system.
5.10.1
Interrupt Handling
The I/O APIC handles interrupts very differently than the 8259. Briefly, these
differences are:
• Method of Interrupt Transmission. The I/O APIC transmits interrupts through
memory writes on the normal datapath to the processor, and interrupts are handled
without the need for the processor to run an interrupt acknowledge cycle.
• Interrupt Priority. The priority of interrupts in the I/O APIC is independent of the
interrupt number. For example, interrupt 10 can be given a higher priority than
interrupt 3.
• More Interrupts. The I/O APIC in the ICH7 supports a total of 24 interrupts.
• Multiple Interrupt Controllers. The I/O APIC architecture allows for multiple I/O
APIC devices in the system with their own interrupt vectors.
5.10.2 Interrupt Mapping
The I/O APIC within the ICH7 supports 24 APIC interrupts. Each interrupt has its own
unique vector assigned by software. The interrupt vectors are mapped as follows, and
match “Config 6” of the Multi-Processor Specification.
Table 5-16. APIC Interrupt Mapping (Sheet 1 of 2)
IRQ #¹
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Via
SERIRQ
No
Yes
No
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
No
Yes
Yes
Direct
from Pin
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes³
Yes
Via PCI
Message
Internal Modules
No
Cascade from 8259 #1
Yes
No
8254 Counter 0, HPET #0 (legacy mode)
Yes
Yes
Yes
Yes
Yes
No
RTC, HPET #1 (legacy mode)
Yes
Option for SCI, TCO
Yes
Option for SCI, TCO
Yes
HPET #2, Option for SCI, TCO²
Yes
No
FERR# logic
IDEIRQ (legacy mode, non-combined or
Yes
combined mapped as primary), SATA Primary
(legacy mode)
Yes
IDEIRQ (legacy mode — combined, mapped as
secondary), SATA Secondary (legacy mode)
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Intel ^® ICH7 Family Datasheet