Re: Help with Zip Drive and the IIgs

[Rubywand <rubywand@swbell.net>]

EDavis writes ...
> 
> More clarification:
> 
> I have an Apple SCSI card.  I have the Syquest drive with a SCSI ID of
> "4", and the Zip is using "5".
> 
> I see that the SCSI card has 4 dip switches, and I don't remember
> setting
> these up when I got the card (circa '90).  I'll look up the owner's
> manual for the card...Could the dip switches need to be set a specific,
> DIFFERENT way to have more than one drive attached???
> 
> Also, Rubywand mentioned that the disks should come pre-formatted.  My
> drive is an external SCSI Zip drive.  It has worked fine with my Mac II
> ci that sits next to my MAIN computer, the IIgs.  After fiddling a bit
> trying to get the Zip drive to work with my IIgs, I reconnected it to
> the Mac, and re-initialized the media on the Mac.  It worked just fine,
> and I was able to save files on the Mac to it.  I then attached it back
> in a SCSI chain to the IIgs, but could not get either drive to work in
> a SCSI chain.
> 
> If I have only the Zip drive attached to the Apple SCSI card, turn the
> termination switch to "on" at the back of the Zip, it is at least
> recognized by the IIgs.  I can boot from the 3.5" drive, and get asked
> if I want to initialize the disk.  I have said "yes" in the past.  As
> the
> Finder comes up, it repeatedly tells me that I already have a disk with
> the name z1 on the desk top, and I need to rename the disk to a
> suggested
> z11.  Then a z12, and so on, until my desktop is full of renamed Zip
> volumes.  (This may have been after attempting to run Advanced Disk
> Utilities, and attempting to partition the volume.)
> ....


     First, it may help to know that many SCSI cards have their own SCSI
ID number. The following info about SCSI ID numbers is from David Empson
...

     SCSI ID 7 is usually special because the Apple SCSI cards are set
to ID 7 by default (and every Macintosh has a hard-wired SCSI ID of 7). 
The only thing that is special about ID 0 is that it is the standard ID
used for an internal drive on a Macintosh.

     There is no problem using SCSI ID 0 on an Apple II. On a RamFAST
SCSI card, it is also safe to use SCSI ID 7 for a drive. The RamFAST
doesn't have a SCSI ID, but every other SCSI card does.


     Regarding the DIP switch settings, the following info for the Apple
High-Speed SCSI card was included in a post by Bradley VonHaden ...


Switch 1 controls DMA: open (up) turns DMA off
                       closed (down) turns DMA on

Switches 2-4 control SCSI card ID: open (up)= "0"
                       closed (down)= "1"

note: 'U' means up (open/0), 'D' means down (closed/1)

The Apple HS SCSI card's ID at the factory* is set to
7 or "111" in binary (switches 2-4 are all Down)


 SWITCH:   234   234   234   234   234   234   234   234
 SETTING:  UUU   UUD   UDU   UDD   DUU   DUD   DDU   DDD
 CARD ID:   0     1     2     3     4     5     6     7*


     If your Apple SCSI card uses the same or similar DIP switch scheme
and has worked okay with your hard disk, then, most likely, the DMA
switch is set correctly. As an Apple SCSI card its SCSI ID number will,
probably, be set to 7.


     Assuming you intend to boot System 6 from your Syquest drive, your
current external device ID's-- the Syquest drive with a SCSI ID of "4",
and the Zip with a SCSI ID of "5"-- are not typical. Usually, the boot
drive has a higher ID number than other connected devices.

     Since most Zip drives allow setting the ID at 5 or 6, this leaves
the following 'normal' setup for your system:

Apple SCSI card- ID 7
Syquest drive-   ID 6
Zip drive-       ID 5


     Regarding the Zip drive "Termination" setting, it seems to be okay
to leave it set to ON whether or not it is physically the last device
plugged in.  The Zip is said to have relatively "weak" termination (i.e.
its termination circuits do not impose an especially heavy load). My Zip
drive is connected between the GS (a RamFAST SCSI card) and a CD-ROM
drive. Its Termination is always ON and it works fine as does the CD-ROM
drive. Since you do not need to worry about flipping Termination, this
makes it easier to swap the Zip between computers.

    "Termination" is just a load. Your SCSI setup must also supply
"Termination Power". Normal, unmodified Apple SCSI cards do not supply
Termination Power; neither does a Zip drive. If your hard disk works
okay, then it seems likely that either it is supplying Termination Power
to the SCSI chain or that your Apple SCSI card has been modified to
supply Termination Power. If the hard disk is supplying Termination
Power, then, its location in the chain may make a difference. My
inclination would be to stick it on the end of the chain. Perhaps
someone with such a setup knows for sure and will post the info.

     You mention that with only your Zip (with Termination ON) plugged
into the SCSI card, you can boot System from diskette and have the Zip
Drive recognized. This does not necessarily mean that everything is okay
in terms of hardware. The Zip cable is short and, even without
Termination Power, you might achieve some level of device recognition
yet still experience glitchy I/O. If the hard disk is supplying your
SCSI Termination Power, it must be ON and included in the chain.


     Another consideration relates to how you start up a system with a
Zip drive. It is a good idea to power ON the Zip drive before powering
ON the computer. Once you get a disk partitioned for ProDOS, it's a good
idea to insert a formatted disk into the powered-ON Zip drive before
powering ON the computer. For now, just insert any blank Zip disk and
answer "No" after booting System when Finder gets around to pestering
you about the unknown disk.


     Concerning Zip disks which have been Initialized via the GS Finder,
the problems you have been having indicate I/O problems with the Zip
drive. It is likely that any disks Inited on the GS are corrupted and
will need to be reformatted.


     Nathan suggests that you may have a bad Zip drive. If rearringing
your SCSI ID's, running with the hard disk in the chain, etc. seem to
get you nowhere, a bad Zip is a possibility to consider. My first Zip
drive was defective; however, unlike yours, it had problems when
connected to the GS _and_ when connected to a PC via Zip's own SCSI
interface card. Three 'obvious' differences I noticed between the bad
drive and the good replacement are:

1. The bad drive was noticeably "noisy"; the good drive makes about as
much noise as a diskette drive.
2. The bad drive ejected disks nearly completely whereas the good drive
ejects them maybe 1/2 inch or so.
3. The bad drive's access was slowed by having to do lots of re-reads
often involving a lot of clattering noise.
  

     Give your Zip a good workout on the Mac-- like, reformat any messed
up disks, copy lots of files to/from the Zip, etc.. If the Zip drive
performs smoothly without any clattering, odd delays, bad copies, ...
then it is likely to be okay.


 
Rubywand