User guide

Figure 8–1 PCI Bus and Interfaces to the I/O Subsystem
PCI Host
Bridge
(21071-DA)
PCI to
Nbus
Bridge
Ethernet
Controller
SCSI
Controller
PCI-VME
Bridge
PCI Bus 32 Bits
VME Connectors
ML013281
Nbus
To the sysBus
(CPU, Memory,
Bcache)
PCI to PCI
Bridge
21052
Option: PCI
Module 1
Option: PCI
Module 2
PMC Adapter
Module
(PMC)
(PMC)
The base address of each PCI device, except the Nbus interface (SIO), is
configured by the Digital Alpha VME 4 firmware. Each base address is initialized
by writing configuration registers located in PCI configuration space of the system
address map.
The following components make up the I/O subsystem and are PCI devices:
• Ethernet controller: interface to the network
• SCSI controller: interface to SCSI devices
• PCI Expansion card: optional interface to PCI devices
• VMEbus interface: See Chapter 10
• Nbus interface: See Chapter 9
8–2 PCI bus