Very Computer

I have a bare 40Mb Quantum 40S drive I took from my Amiga, and want to
connect it to a friend's Mac Plus.

I was under the impression, that I just needed the right cables to go
from the bare drive to the SCSI port on the back of the Mac - but I was
talking to some mac techie guy today, and he said it was impossible
unless the drive had some "logic board" on it... he said it probably
wouldn't since it was from a standard Amiga SCSI controller.

He says not all SCSI drives will connect straight to a Mac.
What was he babbling about? Any help appreciated.
--
Karl Jeacle,                  //

What indeed ? What folly doth this 'techie' person preach.
Yea verily thou canst drive a Quantum from a Mac. I should know,
I done it myself.
I took a Quantum 40Meg from a NeXT cube that was being upgraded, put it in
the case of a Jasmine (after heaving the yuccy Miniscribe), connected it
to the back of a Mac LC with a normal SCSI cable and used DriveStyler (Tee eM)
 to format and partition the disk. It worked great first time ! The Mac was
running system 7 even.
A company called DriveSavers supply this s/w on Jasmine disks that they have
saved from oblivion, they can be contacted on (415) 883 4232.
I see no reason why you should'nt be able to connect your Quantum to a Plus
(provided you have a power supply and SCSI cable) and format the disk with this
software. My guess is that the SCSI controller on the Quantum will do OK
on the Plus.

Give Drivesavers a bell, I would.

Erm, the Mac Plus is a little stupid SCSI-wise, I believe. I've tried
attaching an HP drive to it with no success (Silverlining didn't see
any SCSI device there) although it was fine on SE/30's.

I *have* attached a Quantum 80 to a Plus, though, without problems.

        Nick.

--
Nick Rothwell,  Laboratory for Foundations of Computer Science, Edinburgh.

~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~
                    "Never lean backwards in a troika."

1. The Mac Plus won't supply power to terminating resistors.  This shouldn't
be a problem, since the Quantum drive should.

2. Apple followed Revision 17A of the SCSI-1 specification when they wrote
the SCSI software for the original Mac Plus ROM.  Soon after this, Revision
17B was approved.  The most important change in 17B was that devices were
required to return a CHECK CONDITION with a sense key of UNIT ATTENTION
on the first command after a bus reset (except for certain commands, which
we don't need to go into here).

This causes a problem because the Mac Plus originally tried something like
this at boot time:

        reset the bus
        for each ID
                try to read sector 0
                if this fails, reset the bus

Note that every attempt to read in this scheme is right after a bus reset.
The read attempts will get a CHECK CONDITION, and the Mac will decide that
there is no drive available.

Later Mac Plus ROMs fixed this by only doing one reset of the bus at
ROM initialization time, instead of resetting the bus after each error.

The Quantum drive obeys Rev 17B, and so will not normally work with the
older Mac Plus ROMs.

However, if you use some utility that lets you issue SCSI commands,
such as SEDIT, you can tell the Quantum to disobey Rev 17B.  Page 39h
of the MODE SELECT command contains a bit that can be set to disable
the generation of the CHECK CONDITION after a bus reset.

                                                Tim Smith