Specifications

AlphaServer 1000A Owner's Guide Configuring • 6-27
Single-Controller Configuration
The base configuration for the system, the single-controller configuration, is shown
in Figure 6-7. In this configuration, the SCSI bus is configured as a purely internal
bus that must be terminated at the rear of the system unit using an external SCSI
terminator and at the StorageWorks backplane using an internal active SCSI
terminator. External expansion from the rear of the system unit cannot exceed the
SCSI bus length limit of one-half meter.
All seven StorageWorks slots are run from the system board wide-SCSI-2 controller,
that is, the same controller that runs the CDROM drive and the tape drive, if one is
installed. The two halves of the StorageWorks SCSI backplane are jumpered
together to form a single backplane. Configuration of all seven StorageWorks slots
to the on-board controller requires the jumper cable. Note that the lowest set of pins
(W1) on the J3 jumper are attached (enabled).
Only seven devices can be connected to the bus. The system reserves SCSI ID
numbers for the CDROM drive (ID 4) and the tape drive (ID 5). Thus, to make
StorageWorks slot 4 available, the CDROM drive must be disconnected; to make
slot 5 available, the tape drive must be disconnected.
Table 6-4 shows the SCSI ID settings for this configuration. The specific features of
this configuration are listed below:
Caution: Avoid bending the SCSI cable when
folding it.
1. One end of the internal 50-pin SCSI cable (17-04233-01) connects to its system
board connector.
2. The SCSI cable CDROM drive connector connects to the rear of the CDROM
drive.
3. The remainder of the cable connects to the rear of the tape drive, if one is
installed, and the bus is terminated by an external SCSI terminator (12-41667-
05) at the rear of the system unit. (See Figure 6-6.)
4. One end of a 68-pin internal SCSI cable (17-04022-02) connects to the 68-pin
connector (J17) on the StorageWorks backplane and the other end to the system
board connector.