User guide

– Up to eight nodes (one interface and up to seven additional DSSI
Devices (RF-series ISEs, TF85s, and adapters))
– Eight data lines
– One parity line
– Eight control lines
DSSI architecture improves system performance as follows.
– Each device queues requests and each performs seek ordering.
– Mass storage devices can act independently, since each device contains
its own controller. Several devices can work simultaneously.
An ISE can maintain connection to more than one DSSI interface. That feature
allows ISEs to be shared by multiple CPUs in a DSSI VAXcluster configuration.
For more information about DSSI VAXcluster configurations and the
advantages of such configurations, see the section on DSSI VAXcluster
capability in your system Operation manual.
4.2 External Hardware Options
The following sections contain information on connecting the external hardware
options to the system unit. The external hardware options for VAX 4000 Model
105A/106A systems include the following:
• DSSI expansion box
• SCSI expansion box
• Q–bus expansion box
• Printers, terminals, modems, and other devices that use asynchronous or
synchronous connectors
Your Digital Sales representative can give you information on how to order
a full range of Digital DSSI and Q–bus expansion boxes, printers, terminals,
modems, and other devices that are compatible with VAX 4000 Model 105A
/106A systems.
4.3 Connecting a DSSI Expansion Box
To attach a DSSI expansion box, see Figure 3–8. (Figure 3–8 shows how to
attach a DSSI cable from either a DSSI VAXcluster or a DSSI expansion box.)
4–4 Hardware Options