MSI G52-MA00628 - Manual (Page 42)

Hardware Setup
2-27
PCI Interrupt Request Routing
The IRQ, abbreviation of interrupt request line and pronounced I-R-Q,
are hardware lines over which devices can send interrupt signals to the
microprocessor. The PCI IRQ pins are typically connected to the PCI bus INT
A# ~ INT D# pins as follows:
Order 1 Order 2 Order 3 Order 4
PCI Slot 1 INT B# INT C# INT D# INT A#
PCI Slot 2 INT C# INT D# INT A# INT B#
PCI Slot 3 INT D# INT A# INT B# INT C#