SCSI questions -- mostly curiosity

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The context of these questions is this: I'm playing with, experimenting
with, and attempting to make use of some retired hardware that was
manufactured about 1997.   I'm doing it for my own edification and enjoyment
and the world's affairs do not depend on the outcome.   Then again, it would
be nice to get a Linux box out of it.

What I have is about a dozen 4 ~ 4.3 GB Wide SCSI hard disks, one CD-ROM,
various cables, and half a dozen adapter cards.  Mostly the cables aren't
very well matched to the set of drives, but right now I have three of the
4.0 G Seagates running on an Adaptec 2940UW on an Intel 440BX mobo with a
Pentium II/450 and 192 MB PC-100 RAM.    The third of the three drives is
currently in the formatting process.

Now some questions and speculation:

(1)  The CD-ROM and one 4.2 GB Quantum HDD fit on a cable that resembles an
IDE/ATA cable but has fifty pins instead of forty and is close to 3" wide.
The three drives I have hooked up now have a 50-pin micro connector and a
1.5" wide cable with much finer wires.  The 2940UW has connectors at the top
edge for both.  Can I put both cables on the one bus card, and will they be
read as part of the same SCSI channel?

(2)  I read on a website earlier today that two computers can share a single
SCSI bus.  So if I put identical 2940 cards in two (or more!) computers,
configure one card as ID 7 and one as ID6, and run a cable between, will
both computers be able to use all the drives on the chain?  I'm thinking
something like this:

CD-ROM with Internal Termination Active, ID 0
HDD (Quantum 4.2 GB), ID 5, FAT 32, Windows 98 boot
Internal cable, 50-pin old style
Adaptec Card in Windows 98 Machine, ID 6
External Cable
Adeptec Card in Linux Box, ID7
Internal Cable, 50 pin micro style
HDD, Seagate/Compaq ST34371W,  ID 1, EXT3, Linux boot and usr
HDD, Seagate/Compaq ST34371W, ID 4, EXT3
HDD, Seagate/Compaq ST34371W, ID 8, FAT32
Active Terminator

Will this sort of setup work?  What issues should I expect to confront?

Thanks, and remember it's all for enjoyment.


Re: SCSI questions, postscript

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P.S. the three Seagate drives are now formatted and Mandrake Linux 9.1
install is in progress.
 (I have 10.1 also, but it doesn't seem to have Tux Racer.)
For now I'm using an IDE CD-ROM set up as primary master.


Re: SCSI questions -- mostly curiosity

Pelysma wrote:
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The cable with the finer wires is 68 pin. You can use 50 pin and 68 pin cables
at the same time on the same bus. In that configuration the adapter is in the
middle of the bus and there should be termination on the end of each cable. When
in doubt use auto termination on the adapter.
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It should work, but you should not attempt to access devices with both PCs at
the same time.
To comply with Adaptec specs you should not use three segments, i.e. two
internal and one external cable at the same time. This rule, along with
termination specs, is often ignored with everything working.
You don't need active termination with a 2940UW. A terminated device on the end
of each cable will suffice.
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                   Mike Walsh
            West Palm Beach, Florida, U.S.A.

Re: SCSI questions -- mostly curiosity

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There's an active terminator built into the end of the cable I'm using,
that's all.  One of the things I'm not sure about is how to terminate/not
terminate at the adapter, but if it doesn't do it automatically, it's
certainly done with software.

Thanks for a lot of good stuff!


Re: SCSI questions -- mostly curiosity

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The cable with the finer wires is 50 pin.  I wish I had a couple of the
analogous 68-pin cables in the box, because a number of the drives have this
connector, and it is also the interface between an old HP server and Compaq
external array in the same collection.

Update:  The computer is now running here next to me with a 4 GB IDE drive,
two of the 4GB SCSI drives, and a CD-RW, but the Linux installation bit the
dust because I needed the box for a completely different project.  It's now
running Win2K for the benefit of my ASP.NET homework.  When the term is
over, Linux gets it again.

Although it takes extra time, I like the way the SCSI drives roll up to
speed one at a time to reduce the load on the PSU.  It has the feeling of a
well-thought-out and well-working process about it.


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