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Hardware Setup
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 “AGP/PCI/USB/LAN” IRQ pins are typically connected
to the PCI bus INT A# ~ INT H# pins as follows:
  Order 1  Order 2  Order 3  Order 4 
AGP  INT A#  INT B#     
PCI Slot 1  INT A#  INT B#  INT C#  INT D# 
PCI Slot 2  INT B#  INT C#  INT D#  INT A# 
PCI Slot 3  INT C#  INT D#  INT A#  INT B# 
PCI Slot 4  INT D#  INT A#  INT B#  INT C# 
PCI Slot 5  INT B#  INT C#  INT D#  INT A# 
PCI Slot 6  INT A#  INT B#  INT C#  INT D# 
USB1.1 Controller 1  INT A#       
USB1.1 Controller 2  INT D#       
USB1.1 Controller 3  INT C#       
USB2.0 Controller  INT H#       
LAN Controller  INT E#       
AGP & PCI Slot 1 & PCI Slot 6 & USB1.1 Controller 1 shared INT A#.
PCI Slot 2 & PCI Slot 5 shared INT B#.
PCI Slot 3 & USB1.1 Controller 3 shared INT C#.
PCI Slot 4 & USB1.1 Controller 2 shared INT D#.