Most other Macintoshes with the exception of PowerBooks, provide
termination power (pin 25). The Macintosh Plus does NOT supply termination
power because of power supply limitations. In a situation where the
Macintosh Plus and the SCSI device don't boot properly, check with the SCSI
device manufacturer to make sure the device is not expecting termination
power from the Macintosh Plus.
Note also that even though the SCSI port is a DB-25 connector, it should
not be used to connect any other serial or parallel devices. ONLY SCSI
DEVICES should be attached to the SCSI port.