User`s guide

Installing Expansion Boards

8-8

Identifying PCI Devices in the SCU

The SCU automatically scans for PCI devices and assigns resources to

them. PCI devices appear in the SCU as either assigned to a slot, or as

embedded devices.

If a PCI expansion board uses one or more interrupts, but none of the

interrupts are shared, then the SCU will contain an entry for each interrupt

used by that PCI expansion board. As an example, the Adaptec 3940W

SCSI controller has a PCI-to-PCI bridge chip with two devices behind it,

each requiring an interrupt. If the expansion board were installed in PCI

Slot 1, the entry in the SCU might look similar to this:

• PCI 1 PCI SCSI Controller IRQ15

• PCI 1 PCI SCSI Controller IRQ14

If a PCI expansion board uses one or more interrupts, but the interrupts

are shared, then the SCU will display an entry for an interrupt in that slot,

and the remaining devices that share that interrupt will be shown as

“embedded” devices. Consider the Adaptec 3985 SCSI controller. This

controller has a PCI-to-PCI bridge chip with three devices sharing one

interrupt and the fourth device using a second interrupt. If this expansion

board were installed in PCI Slot 4, the entry in the SCU might look similar

to this:

• PCI 4 PCI SCSI Controller IRQ10

• PCI 4 PCI Memory Controller IRQ2(9)

• Embedded PCI SCSI Controller

In this case, the two interrupts are shown, with devices sharing the

interrupt shown as embedded devices.

Onboard devices always appear as embedded devices. The onboard VGA

controller, as an example, would appear as:

• Embedded VGA