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From: km@cadre.dsl.pitt.edu (Ken Mitchum)
Newsgroups: comp.periphs
Subject: Re: Problem with Mac Plus booting off a Newbury drive
Message-ID: <1989Sep13.173738.2923@cadre.dsl.pitt.edu>
Date: 13 Sep 89 17:37:38 GMT
References: <3436@deimos.cis.ksu.edu>
Reply-To: km@cadre.dsl.pitt.edu (Ken Mitchum)
Organization: Decision Systems Laboratory, Univ. of Pittsburgh, PA.
Lines: 19

>My Mac Plus simply refuses to boot off of my Newbury 3380 drive.  As I
>understand it, the Mac Plus does not provide power on the SCSI bus and if
>a drive is depending on SCSI bus power for termination, it will not be
>recognized?!!

The problem with Newbury drives and the MacPlus does not have anything to do
with the source of +5 volts for the terminating resistors, which should be
the drive. The problem with the MacPlus appears to be that the Newbury
drive spends an inordinate amount of time doing self-testing on powerup,
and ends up sitting on the SCSI bus. This is not appear related to the
infamous "unit attention on reset" problem, as it still occurs when unit
attention on reset is disabled, and with new Mac roms. The drives work fine
with newer Macs, which apparantly recover and reset the bus. My solution
was to simply boot the MacPlus from a floppy, then switch to the hard disk.

 Ken Mitchum
 Decision Systems Labs
 Univ of Pgh
 km@cadre.dsl.pitt.edu