🚀 go-pugleaf

*****************
SCSI HELL: THANKS
*****************

I wish to thank the many people who offered me advice regarding my trip to
Scuzzy Hell. I got too many responses to write to individually (??!).
Definitely the first time that's ever happened to me in three years on the
Net, and a nice thing to remember. 

I tried everything that was offered as advice, though not all possible
permutations. Keeping the original configuration [7100 --> Zip drive -->
Epson 1200C scanner], but with a Digitally Active Terminator and APS
cables finally seems to have done the trick. At least, still waiting for
the blowup -- will be looking askance at SCSI equipment for a long while
to come. Now feel that every SCSI peripheral should be shipping with a
DAT. At least a warning sheet -- "You have purchased a SCSI device --
please be prepared for any contingency."

Most interesting to me was that _every single person_ seems to have a
_different_ recipe as a solution. To the individuals who referred to a
"SCSI standard," I just had to laugh. That's clearly an oxymoron.

The original question probably should have gone to the group
comp.periphs.scsi; I am posting the summary there now as it may be of
interest to someone.

Disclaimer:
FWIW, YMMV & caveat emptor -- I'm as knowledgeable about the techniques
and products mentioned below as I am about brain surgery, and do not
warrant any one over another.

craig j
cart@umich.edu



*************************
SCSI HELL: ADVICE SUMMARY
*************************

>When I got the scanner, thought I could just turn off the Zip termination
(a switch), hook up a cable from the Zip to the back of the scanner, turn
on the scanner's SCSI termination (also a switch). Nothing could be
simpler, right? Well, the SCSI cable that shipped with the unit was 50-pin
to 50-pin, and I needed a 25-pin to 50-pin to work with the Zip. So I went
out and bought one (Belkin, 6-foot).

ran into something similar (2 internal drives, DAT tape drive, scanner,
200 Mb Syquest)

The scanner wanted to be the first one connected to the mac. 

The other thing to try is to get an active terminator. This solved a
different SCSI problem for me (it did not involve a scanner, it was an CD
ROM drive that I mounted myself). It drove the CD Rom drivers, hard disk
formatting software and Retrospect nuts until I turned on the Active
Termination on an APS HyperTape.

*************************

FWIW, I went thru a SCSI problem last summer. My set up was internal drive
- Zip drive - external drive - scanner. Disconnected the Zip to use with
my PowerBook. Reconnected it and the next time I went to use my scanner it
didn't show up. Assumed that the driver went bad, so I reinstalled. Still
nothing. Started checking termination and all seemed to be well, so I
started playing with chain order. Turned out the problem was a blown SCSI
controller on the external drive. Fortunately it was still under warrenty.
Since then, I've added an external CD drive and have it at the end of the
chain because it has the mini SCSI-2 connectors and I didn't want to buy
another cable. Everything works well, even with the scanner off, and to be
honest, I'm not sure about the termination status of the scanner, as it's
done internally and I bought it used. Don't know if there is a way to
check for intermittent problems with a SCSI controller. 

*************************

In article <cart-0402961906430001@pm056-19.dialip.mich.net>,
cart@umich.edu (c art) wrote:

>Yes, I double-checked all the IDs with SCSI Probe: Hard drive 0
>CD-Rom  1
>Scanner 2
>Iomega Zip 5
>CPU  7

>Total length of external SCSI cables: 3 + 6 = 9 feet. 

You've got at least a couple of feet of SCSI cable inside your Mac,
bringing your total to 11 feet. I think that the maximum length you can
have is 8 feet per chain. [NOTE: see following comment.]

And even at that length, make sure you have high quality cables.

I once tried to install an external hard drive and a tape drive onto a PC
Novell file server. I was just under 8 feet but I had tons of data
corruption problems.

I would recommend a 3 foot cable to the Zip and then a 1 foot cable to the
scanner.

*************************

Max length on an SCSI chain is 6 meters, about 18 feet. There is less then 1 
foot of cable internally on most macs. Buy some good cables, get a good 
terminator. Some devices may need to have termination before the device to 
work properly. Get a good pass through terminator. If any of the devices on the 
chain are selectable for termination power, jumper the last device in the chain 
to supply termination power and all others to not supply termination power. 
Switch the order of the devices. Pray hard.

*************************

I recently bought a 1GB Quantum HD from La Cie and installed it in the
CD-ROM bay of my Quadra 610. It was a perfect installation although I did
go ahead and use the thin internal SCSI cable to plop the new drive
between the Conner 160 HD and the motherboard. Well right from the start
my Mac did all sorts of silly things, most of which concerned a consistent
subset of my applications crashing shortly after start-up, even if they
were located on the original HD and not the new one LOL.... I reformatted
the new drive but couldn't get Apple HD SC Setup nor La Cie's utility to
update the driver software. The drive was shipped formatted and "ready"...

Anyway after wondering about buying a new SCSI cable to replace the
internal one I finally found an application which would completely erase
the formatting AND the driver on the HD (Micronet Utilities 6.0.2 did the
trick and I owe them my butt....). Then I used La Cie's formatting utility
Silverlining to put a fresh format and driver on the Gig.... and voila, it
wasn't extension conflicts, it wasn't termination, it wasn't the cable, it
was that danged driver... How it caused all that havoc, I have no idea,
but i do know what fixed the problem.

So if you get the short, high-quality cables, and your SCSI is still
biting you in the butt, have a look at your drivers, by all means.

*************************

Go on over to < http://www.apple.com > and then into product support and
the Technical Info library. Look for a paper on scsi.

According to apple, your internal CD drive id should be set to 2.

The scanner should be a higher number and should be the first device on
the chain, although tis is not necessarily true.

You are correct in making ALL scsi cables the same length and manufacture.
Do not cheap these. Get the best you can. Also an active terminator from
APS is a good idea.

Hang in there - pray for "Firewire"

*************************

> Not that I believe you, but if apple wants internal CD drives set to 
> SCSI ID 2, why do they all come from the factory set at 3?

I have absolutely no idea!

I was merely quoting from Apples own Technical Library Notes about scsi.

Huh - Hunh??

*************************

>After years of hearing about SCSI Hell from others, since the recent
purchase of a scanner (Epson 1200c) I'm finally getting toasty myself! 

I had exactly the same problems with my 7100/66 that you are having. I got
mysterious "disk errors" and sad macs which caused my internal HD to crash
big time, and I could only resurrect it after zapping the PRAM and
reformatting.

I was using an external HD and external CD daisy-chained together. After
talking to about a dozen tech support people, I learned that, yes,
mismatched or cheap cables CAN and DO cause massive errors and data loss
like I experienced. It comes from electrical impedance problems, I was
told by an Apple tech.

My recommendations:

1) Buy all of your cables from the same place, all the same brand. APS or
Apple (more expensive) cables are the best and most reliable. You can
connect the Zip using a 25-25 pin (APS sells them) from the computer, and
daisy-chain it with a 25-50 from the Zip to the next SCSI device, for
example.

2) Don't use the Zip's termination. I've heard bad things about it, and I
know from my experience that 7100's are especially finicky when it comes
to good termination. You really should buy a Digital Active Terminator
(DAT) from APS. The last device on my SCSI chain is an APS drive, which
came with the DAT internally.

And for Pete's sake, avoid at all costs those silly "thin" SCSI cables.
They're nothing but trouble!

I use nothing but APS cables (reasonable prices, great tech support) and I
haven't had a single problem since. My SCSI chain has grown, too: I now
have an external HD, CD, Scanner, SyQuest AND Zip, and still not a
problem!

>Also, the Epson scanner manual has a note that cryptically says "If you
are connecting the scanner to a SCSI device other than the computer, use a
cable with 50-pin connectors on both ends." 

I think this manual just assumes that you are going from the scanner to
another 50-pin device, in which case you would use a 50-50 SCSI
daisy-chain cable. You can use a 50-25 to chain the scanner and Zip
together.

It took an investment in cabling, but my SCSI chain is perfectly happy.
Good luck with yours!

*************************

Just for the heck of it, you might try both changing relative positions of
the devices, the SCSI ID's, or if these don't work and you've already
verified the cable integrity, as a last resort you could add termination
in addition to the standard beginning/end of the chain. I know you're not
supposed to do this but it has worked for me before although I eventually
figured out a configuration where I didn't have to do this. Also, APS
sells something called a SCSI Sentry which is supposed to clean up SCSI
problems by regulating the power on the line. You might want to try it. 

*************************

I bought a Relisys AVEC 2400 in November and went through hell too,
although my hell was gentler than yours. I tried all the usual home
remedies. What finally worked for me was to be sure that only ther Mac CPU
had a higher SCSI address than the scanner. The Mac's SCSI address is 7,
so I set the scanner's address to 6. Magically, I've had no trouble since
then. Does that make sense? Of course not. But it's SCSI, so sense is
meaningless. Give it a try.

My scanner also sits at the physical end of SCSI cable chain, but that
didn't help until I set it to address 6. 

Another thought....

>Yes, I double-checked all the IDs with SCSI Probe: Hard drive 0
>CD-Rom  1
>Scanner 2
>Iomega Zip 5
>CPU  7

If the SCSI address selector switch on the scanner is not making firm
contact, then address 2 would "unmake" into address 0, the disk! That
would lead to the symptoms you report, since the finder would get replies
from two devices in any attempt to communicate with the HD. 

I LOVE that diagnosis. I bet that's it!

*************************

>Well, got this queasy feeling. If the problem _isn't_ the cable, I don't
have a clue what it is! How can simple cable connection be this
complicated? Is there a way to examine a SCSI chain in more detailed
fashion than SCSI-Probe? Could it be a System problem? Could it be ...
Satan?

FWB's Hard Disk Took Kit has more stuff than SCSI-Probe. And if it was
Satan he'd disable your "Save" command as well. 


>Also, the Epson scanner manual has a note that cryptically says "If you
are connecting the scanner to a SCSI device other than the computer, use a
cable with 50-pin connectors on both ends." Huh? Can't tell from the
manual if this is a requirement or a suggestion. Does anybody know? Does
this mean I can't daisychain it with the 50-pinless Zip? Do I buy _two_
25/50 pin connectors and put the Zip at the end? 

It shouldn't matter if it's a requirement or a suggestion, if it's broke
now you might as well try it. Seriously though, we've had problems
connecting a SyQuest 270MB and a scanner to a 8100/100. Simply reversing
the order (computer--->scanner--->syquest) seemed to do the trick. Now it
only crashes "less often." Just don't forget to terminate the Zip and not
the scanner.

*************************

Dear queasy... Zip drives haven't been too reliable. Try disabling your
Zip drive extension (forgot the name of it) and just disconnecting the
drive. If the Scanner works OK then call whoever you got the zip from and
get another. Sounds to me like you got termination probs (as you probobly
have guessed) and they are probobly related to that Zip drive. You might
try putting the Zip at the end or turning both termination switches on or
off at the same time. SCSI is sorta like VooDoo. Keep chanting till it
works then don't touch it.

I had a similar problem with a customer the other day and it turned out to
be (yet again) the Zip drive. I don't know what it is about those things
but they don't seem to play nice with the SCSI bus. 

*************************

I agree that likely causes for your SCSI problem include: 

1. Cable too long
2. Defective cable

If you still experience problems with your new 3 foot cable another cause
to consider is:

3. Defective termination switch on your scanner 

If you have an external terminator or can borrow one, you can test for
this. With Mac and external devices powered off, turn your scanner
termination switch off and plug the external terminator into the free SCSI
port of your scanner. If this doesn't solve the problem other common
causes for SCSI problems are:

4. Mixing cable types, The scanner itself 

Cables from different manufacturers and even different styles from the
same manufacturer have varying types of construction, impedance and wire
placement. This may cause SCSI problems. Since you have an Iomega Zip
Drive, the 25 -25 pin Iomega cable will automatically be from a different
vendor than your 25 - 50 pin cable.

Anecdotally, scanners cause more SCSI problems than other external devices. 

The only way I know of that can correct the mismatch in impedance from
different manufacturers cables or termination problems from a scanner is
the active terminator called SCSI Sentry from APS Technologies at
800-304-9074. It costs $39.95 plus shipping. I cannot guarantee that this
will solve your problem. Having experienced "SCSI hell" myself, all I can
say is that it worked for me. And I didn't need to buy the optional $19.95
power adapter. SCSI Sentry worked fine on the power coming through the
SCSI cables from my Mac.

Hope this helps.

*************************

Get an active terminator. It will solve all your SCSI problems.

*************************

>After years of hearing about SCSI Hell from others, since the recent
purchase of a scanner (Epson 1200c) I'm finally getting toasty myself! 

You have already been given some great advice in this thread. But if you
want to eliminate *any* possibility of cables being the source of your
woes, try Granite Digital cables. They also make active terminators and
lots of neat gizmos. Call them @ 510-471-6442 or FAX @ 510-471-6267. I
have run into bad Apple cables, bad APS cables and lots of bad cheap
cables. Granite Digital cables are expensive and worth every penney. Throw
out all your old ones (or give them to a friend who uses a PeeCee) and buy
all you need from Granite. I don't work for them either, I just swear by
their cables. 

*************************

I have to concur with this. While I don't know anything about Granite
Digital and their cables, I have learned through bitter experience that
SCSI cables are no place to economize. Buy the best cables you can find,
and keep a spare around since even expensive cables will all the sudden go
bad at the most inconvenient moment.

*************************