CAUSE: Macintosh Plus boot ROM checks the SCSI port upon
boot-up. If there is a SCSI device connected, the Macintosh
tries to communicate with it. Of course, if the device is off, it
will not respond and the Macintosh Plus will hang while it is
waiting for a response from the SCSI device.
CURE: Disconnect the deactivated SCSI device or turn it on.