BOXD946GZISSL Intel (CPU), BOXD946GZISSL Datasheet - Page 49

• Manufacturer Part Number: BOXD946GZISSL
• Manufacturer: Intel (CPU)

Specifications of BOXD946GZISSL

• Lead Free Status / RoHS Status: Compliant

2.6
This section describes interrupt sharing and how the interrupt signals are connected
between the PCI bus connectors and onboard PCI devices. The PCI specification
specifies how interrupts can be shared between devices attached to the PCI bus. In
most cases, the small amount of latency added by interrupt sharing does not affect
the operation or throughput of the devices. In some special cases where maximum
performance is needed from a device, a PCI device should not share an interrupt with
other PCI devices. Use the following information to avoid sharing an interrupt with a
PCI add-in card.
PCI devices are categorized as follows to specify their interrupt grouping:
•
•
•
The ICH7 has eight Programmable Interrupt Request (PIRQ) input signals. All PCI
interrupt sources either onboard or from a PCI add-in card connect to one of these
PIRQ signals. Some PCI interrupt sources are electrically tied together on the board
and therefore share the same interrupt. Table 14 shows an example of how the
PIRQ signals are routed.
Table 14. PCI Interrupt Routing Map
NOTE
In PIC mode, the ICH7 can connect each PIRQ line internally to one of the IRQ signals
(3, 4, 5, 6, 7, 9, 10, 11, 12, 14, and 15). Typically, a device that does not share a
PIRQ line will have a unique interrupt. However, in certain interrupt-constrained
situations, it is possible for two or more of the PIRQ lines to be connected to the same
IRQ signal. Refer to Table 13 for the allocation of PIRQ lines to IRQ signals in APIC
mode.
PCI interrupt assignments to USB ports and Serial ATA ports are dynamic.
PCI Interrupt Source
SMBus controller
ICH7 LAN
PCI bus connector 1
PCI bus connector 2
INTA: By default, all add-in cards that require only one interrupt are in this
category. For almost all cards that require more than one interrupt, the first
interrupt on the card is also classified as INTA.
INTB: Generally, the second interrupt on add-in cards that require two or more
interrupts is classified as INTB. (This is not an absolute requirement.)
INTC and INTD: Generally, a third interrupt on add-in cards is classified as INTC
and a fourth interrupt is classified as INTD.
PCI Interrupt Routing Map
PIRQA
PIRQB
PIRQC
ICH7 PIRQ Signal Name
PIRQD
INTC
PIRQE
INTA
INTD
INTC
PIRQF
INTA
INTB
Technical Reference
PIRQG
INTB
INTA
PIRQH
INTC
INTD
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