Intel AN430TX - Motherboard - ATX Technical Product Specification page 52

AN430TX Motherboard Technical Product Specification
Now, however, plug an add-in card that has one interrupt (group INTA) into the first PCI slot.
Plug a second add-in card that has two interrupts (groups INTA and INTB) into the second PCI
slot. INTA in the first slot is connected to signal PIRQA. INTA in the second slot is connected to
signal PIRQB, and INTB is connected to signal PIRQC. With no other cards added, the three
interrupt sources on the first two cards each have a PIRQ signal to themselves. Typically, they will
not share an interrupt.
NOTE
The PIIX4 can connect each PIRQ line internally to one of the IRQ signals (3,4,5,7,9,11,14,15).
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.
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