#HARD DRIVE HELP
4 messages in this thread
I need help getting a SCSI hard drive to work with my system.
Description of my system: Amiga 500, Standard 512K Agnus, A501 chip,
additional 2 megs on Supra 500xp 40 meg hard drive, CSA Mega Midget 68030,
68882, MMU, with 512K 32 Bit SRAM. Workbench 2.0.
I am trying to daisy chain a Hard drive that came out of a stock MAC IIci. It
is a Quantum Pro Drive 80S (80 megs). It is in its own cabinet with power
supply and controller. I have a straight through cord with all 25 pins, which
is what I was told I needed.
When I hook it up my A500 will not boot. The screen stays white and both drive
lights on both drives light up. I have tried changing the ID number of the
Quantum drive. Even when just the cord is hooked up, nothing happens.
I talked to a dealer (at home, he is out of business) and said that I needed to
make sure that the termination is off on the Supra and on on the Quantum. I
can't find imformation in the Supra manual about termination. He also said
that there is not a high degree of success rate in hooking up extra drives.
I haven't done anything to my startup sequence, but I figure that is not my
problem… maybe I'm wrong.
I would appreciate any detailed "step by step" help if available. Thanks.
Steve Canham 74223,2262
Steve,
There are usually two things to take care of when installing a chained
hard drive. The first is termination and the second is the drive's SCSI id. It
is very likely that the first hard drive is jumpered as SCSI id=0 or id=6,
depending upon how the manufacturer set the drive in the subsystem. If you run
HDToolbox or whatever scsi formatting software you have, you will find out what
the drive id is. You MUST set the SCSI id of the second drive to an id
different from the one used for the first drive. Most Mac subsystems have a
pushbutton wheel switch on the rear of the drive case. By pushing the button
you can move the wheel to whichever id you want to use. The wheel will have
numbers ranging from 0 to 7. You can use any one but id=7, which is reserved
for the controller in the Amiga drive system. Given that id=0 or id=6 is
typically used for Amiga subsystems, you would probably be safe with id=1 or
any number other than 7 and the id indicated by your format software.
The second problem is termination. Since the Amiga subsystem contained
only one drive, that drive is terminated. Because the Mac subsystem contains
only one drive it may or may not be terminated. Some Mac subsystems use a
terminator block which is connected to the spare SCSI connector on the rear of
the cabinet. Since the Mac drive will be at the END of the SCSI chain it MUST
be terminated, but the first drive's termination MUST be removed. To
accomplish that you need to open the Amiga drive case, remove the screws used
to mount the drive and turn the drive over so you can see the PCB on the
underside of the drive. Look carefully to find the various jumper sets either
on the bottom of PCB or along side the 50-pin SCSI connector. You are looking
for a set of jumpers, either in a set of 3 or 4. If you look carefully at the
jumper set you might find some numbers silk-screened along side each jumper
pair with the numbers 0, 1, 2 or 0, 2, 4. Those will most likely be the jumpers
for setting the SCSI ID. You can change those if you want, but I would leave
the SCSI id alone. Now, somewhere adjacent to the 50-pin SCSI connector on the
drive you will see two or three resistor packs. They will be located very
close to and parallel to the SCSI connector. These are the terminating
resistors. To un-terminate the drive you need only remove the resistor packs.
Use some Scotch tape to tape the resistor packs to the top of the drive so you
don't lose them.
That un-terminates the drive in the Amiga subsystem. More than likely
the Mac drive is already terminated either by a terminator block installed on
the external spare SCSI connector on the rear of the case or the drive itself
is terminated in the same way as the Amiga drive described above.
Unfortunately, you cannot know exactly how the Mac drive's termination has been
handled. The vast majority of Mac subsystems rely on the terminator block
because that is sort of the Mac standard approach. If you don't have a
terminator block you can buy one at a Mac dealer such as CompUSA.
Hope this helps. If it all sounds like more than you are prepared to
try, I would take the whole thing to a knowledgeable Amiga dealer. The one you
mentioned in your message obviously doesn't know much about hard drives.
Steve,
Your dealer/friend is correct. You need to remove the termination
resistors on the Supra and make sure they are on on the Quantum.
Also, make sure that your cable is as short as possible. The 25 pin
cables are not very reliable. And make sure it's a SCSI cable, not a 25 pin
serial cable. In a true 25 wire SCSI cable, each wire is individually
shielded.
Don
Sounds to me like you might have an improperly wired cable. You say it's a
25 pin straight through… but most of the MAC external HD's I've seen use
the 50 pin 'Centronics' style connector on the HD end. The Mac has the
25-pin end. You might try lifting pin 25 (of the 25 pin end) This signal
is 'termination power'. When using a powered external box, both it and the
computer could be driving the line. That should be OK, but I've seen some
controllers where it caused problems.
Jim
MOS via Autopilot & Amiga