Intel Desktop Board D845EPI Technical Product Specification
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Table 16. PCI Interrupt Routing Map
ICH4 PIRQ Signal Name
PCI Interrupt Source
PIRQA PIRQB PIRQC PIRQD PIRQE PIRQF PIRQG PIRQH
AGP connector INTA INTB
ICH4 USB UHCI controller 1 INTA
SMBus controller INTB
ICH4 USB UHCI controller 2 INTB
AC ’97 ICH4 Audio/Modem INTB
ICH4 LAN INTA
ICH4 USB UHCI controller 3 INTC
ICH4 USB 2.0 EHCI controller INTD
PCI bus connector 1 INTD INTA INTB INTC
PCI bus connector 2 INTC INTB INTA INTD
PCI bus connector 3 INTD INTC INTA INTB
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NOTE
In PIC mode, the ICH4 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 15 for the
allocation of PIRQ lines to IRQ signals in APIC mode.