From: unseen@mcl.ucsb.edu (Charles F. Kane)
Newsgroups: comp.sys.amiga.misc,comp.sys.amiga.hardware,comp.sys.amiga.tech
Subject: ***SCSI DAISY-CHAINING PROBLEMS***, continued...
Date: 12 Jan 93 07:24:59 GMT
Article-I.D.: mcl.unseen.726823499
Followup-To: comp.sys.amiga.misc



Here's an update for those interested (sorry, my last update didn't
have the vital stats):

I'm trying to add a second SCSI hard drive to my system, but am encountering
all sorts of problems.
SYSTEM:
-----A500 w/ 5 megs ram, Supra SCSI interface (the old style with
separate interface and hard drive cases), Quantum 85Meg HD.
TRYING TO ADD:
-----Seagate ST157N HD.

Both HDs have their own power supplies. The interface does not.

Here's what I get:
When I connect the Seagate onto the daisy-chain port of my Quantum case,
the system will boot, and work correctly for a few minutes. Then disk
errors start to occur when I try to read or write to disk. They become
more and more frequent, until I can no longer do anything. The really
strange thing is that these errors not only occur on both hard drives,
but on my two floppy drives as well. There are all kinds of errors:
read, write, bad header, key not set, etc.

I've tried playing with the SCSI terminators, with no luck. The only way
the system seems to work at all is when both hard drives have the
terminators in. Without them, the system won't even boot.

The SCSI numbers are OK. The first drive is SCSI 0, the second is SCSI 1.

Some theories (from others and from myself):

1. Thermal problems.  The time delay indicates some chip might be
overheating.

2. SCSI terminators improperly configured. Again, I've tried playing with
them with no luck. (There are some combinations I have yet to try, but I'm
guessing that a terminator problem would not let me boot AT ALL, rather
than throwing oddball errors at me after a while. And why would it screw
with the floppies?)

3. Bad CIA chip? I don't know anything about this one, but one person
suggested it. Any ideas on this one?

4. Crappy SCSI interface. Lotsa people bitch about Supra hardware. I've
always liked this interface, never had any problems with it, but it IS
pretty old....  Maybe I'll try Supra Tech support. Course, they probably
never even heard of my antique... :\

5. Insufficient power. Both HDs have their own power supplies, but I
doubt if the interface, which is attached to the side expansion slot
of the A500, can draw power through the SCSI line to it's HD. Adding
another HD would theoretically increase the power load on the inter-
face (?).  To test this, I disconnected the two meg ram expansion, and
the external floppy, but the same problems occurred.

6. Other. Insert your best guess here.

Well, that's the sitch.  I've gotten a lot of helpful responses, and have
learned far more about SCSI devices in the last week than I've ever
WANTED to know.

Any brilliant technical wizards out there with ideas bursting forth
to permanently fix all the problems? Any not-so-brilliant hardware
kludgers who can suggest a temporary hack to sort of work around the
problem? Any half-wit McDonald's fry chefs who can tell me "Dude, like,
yer SOL, y'know?"

I'll accept anything at this point.

			-Charles Kane (unseen@mcl.ucsb.edu)

p.s. On a side note, I tried daisy-chaining an old Seagate 20meg HD
onto the Quantum. That has been a complete failure so far, but I
haven't experimented much with it yet. More updates to come, so stay
tuned for

ARNOLD SWARZENEGGER AND A HOST OF SCSI TERMINATORS, Part IV!!!
Newsgroups: comp.sys.amiga.misc