Specifications
APPENDIX A
SCSI TERMINATION
A.1SCSI TERMINATION USING EXTERNAL TERMINATOR OPTION
The preferred method of terminating the SCSI bus in an AMOS based computer is the
installation of an external terminator. In early April of 1993, the external SCSI bus
terminator became standard on all AMOS based computer configurations. Using an
external terminator makes the task of installing an add-on subsystem (like a portable
CD-ROM drive) easier, eliminating the necessity of removing terminators from a SCSI
device located in the host computer.
The AM-137 board is sensitive in regards to SCSI bus termination. If you are using the
external terminator and one of the SCSI devices inside your computer also has its
terminators installed, you may experience problems.
The SCSI bus must be terminated at each end of the cable. The AM-137 board
terminates the SCSI bus at one end of the 50-pin interface cable. Termination at or
close to the other end of the SCSI bus is required, either via an external terminator or
via a terminator installed on the SCSI peripheral nearest the end of the bus.
External terminators are available from Alpha Micro under part number PRA-00222-00;
an external terminator is included in the AM-137 upgrade kit.
To use the external terminator, you need to insure none of your SCSI peripherals inside
the computer are terminated. You will also need to follow the guidelines in the section
on providing termination power for the SCSI bus.
The external terminator is shown in the illustration below:
PDI-00137-50, Rev. A01