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1.2.1.5 Embedded DSSI Host Adapters
Your system has two Digital Storage Systems Interconnect (DSSI) adapters
built into the CPU. The DSSI adapters provide a path to two separate DSSI
busses (Bus 0 and Bus 1) through which the CPU can communicate with
DSSI devices. Each DSSI adapter can support seven DSSI devices.
The DSSI host adapters also allow you to link one of the DSSI busses to a
second host to form a dual-host configuration. When a DSSI bus is extended
to a second system, both systems can share up to six DSSI devices. Refer to
Section 1.3 for further discussion of DSSI VAXcluster or dual-host systems.
1.2.2 Optional Components
System options can include multiples of components that are part of the
base system (for example, additional memory modules or ISEs) and the
following kinds of options:
•
Mass storage devices and controllers
•
Mass storage subsystems
•
Mass storage expanders
•
Communications controllers and adapters
•
Real-time controllers
•
Printer interfaces
1.2.2.1 Mass Storage Devices and Controllers
Mass storage devices record data on magnetic media. The data recorded is
not lost when you turn off the system, but can be altered or erased if you
record over the data. Use mass storage devices to store data and software
permanently. When the data or software is needed, the CPU transfers it
from the mass storage device into main memory. The two primary types
of mass storage devices are the RF-series ISEs and devices with removable
media, such as tape cartridges and compact disks.
Integrated Storage Elements
Up to four RF-series ISEs can be installed in your system. An ISE is
an intelligent storage device that contains its own controller and server.
Special mounting hardware allows the device to plug directly into the
BA400-series backplane.
Devices with Removable Media
Devices with removable media, such as tape cartridges, are used as both
input and output devices. In addition, compact optical disks are used as
System Overview
1–21
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