MSI MS-6551 - CNR (Communication Network Riser); PCI Interrupt Request Routing

Chapter 2
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expansioncard to make any necessary hardware or software settings for the
expansion card, such as jumpers, switches or BIOS configuration.
CNR (Communication Network Riser)
The CNR slot allows you to insert the CNR expansion cards. CNR is a
specially designed network, audio, or modem riser card for ATX family
motherboards. Its main processing is done through software and controlled by
the motherboard’s chipset.
ISA Slot
The ISA slot allows you to install the ISA expansion card.
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 F# pins as follows:
Order 1 Order 2 Order 3 Order 4
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#