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Page 4 Installation Instructions: AM-65X 1/4" Streaming Tape Drive

PDI-00651-00, Rev. A01

Setting the SCSI ID

Each SCSI device attached to the SCSI bus must be set to a unique address. Two SCSI devices cannot

share the same address. The AM-65X is a Wide SCSI-2 device, and can therefore be set to any SCSI ID

from 0 through 15 (except 7, which is reserved for the SCSI controller). On the narrow SCSI bus

supported on AMOS computers prior to the AM-6000 (and optionally on the AM-6000), you can use

only IDs 0 through 6. Figure 1 shows the jumper settings for each SCSI ID.

SCSI BUS TERMINATION

To function properly, the SCSI bus on your computer must be terminated at each end. The SCSI

controller terminates one end of the bus; the opposite end of the bus can be terminated in one of two

ways: 1) using the preferred method—an external terminator, or 2) installing on-board terminators in the

peripheral that's at the other end of the SCSI cable. If the AM-65X is the last physical device on your

SCSI bus, you must use an external terminator, since the AM-65X does not provide for SCSI termination

resistors.

External SCSI Bus Termination

The preferred way to terminate the SCSI bus in an AMOS computer is to install an external terminator.

Using an external terminator makes it easier to install an add-on subsystem (like a portable CD-ROM

drive), eliminating the need to remove terminators from a SCSI device inside the computer.

The AM-65X is very sensitive to termination issues. Any computer with an AM-65X installed

requires active termination of the SCSI bus. All computers that are supported with the AM-65X

are supplied with active terminators.

External active terminators are available from Alpha Micro under part numbers PRA-00222-20

(wide active terminator) and PRA-00222-21 (narrow active terminator).

To use the external terminator, you need to insure that none of the SCSI devices inside the computer are

terminated. You also need to follow the guidelines in the section on providing termination power to the

SCSI bus, below.

10 and 21-slot rack mount VME computers have no external SCSI connector. To install an external

terminator, you need a special adapter cable, DWB-10200-01. The connector on this cable is compatible

with the external terminator and also allows you to easily attach a portable CD-ROM drive or other SCSI

device.

Figure 2 shows both narrow and wide SCSI terminators:

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Alpha Microsystems AM-649 Bedienerhandbuch Seite 7