rankins@argentina (raymond r rankins) (08/18/90)
Does anyone have a schematic or some sort of diagram or instructions for
building an Apple compatable SCSI Terminator? This is for an Apple IIGS
with Apple's SCSI card. I can't see paying $15 to $30 for something
that probably costs about $5 in parts.
Anyone have any they want to sell cheap?
I am putting together a case with Quantum SCSI drive and a 3M tape drive
in it. What is the best way to wire this up and terminate it? Someone
recommended that the tape drive be at the end of the SCSI chain. Here is
what I've come up with so far: ([] = 50 pin Centronics connector)
SCSI in SCSI out
[] [] [] [] []
\ / \____/\ \
\ _____ / \ _____ \ _____
\/ \/ \/ \ \/ \
_||_ _||_ _||_ _||_ _||_ _||_
| | | | OR... | | | | OR... | | | |
| | | | | | | | | | | |
| | | | | | | | | | | |
| | | | | | | | | | | |
|____| |____| |____| |____| |____| |____|
Disk Tape Disk Tape Disk Tape
Fig. 1 Fig. 2 Fig. 3
I believe someone posted in comp.periphs.scsi that Fig. 1 is the
proper way that a case should be wired. If so, is it okay just to
install the resistor packs directly on the tape drive to terminate the
SCSI bus? Would I need any further termination like on the SCSI out
connector in Fig. 1?
Fig. 2 doesn't seem at all right for a bus system like SCSI, but
that's the cable set up that came with the case. Where would you
place the terminators in a set up like that? Which connector should
be the SCSI in, or doesn't it matter?
If I don't care if the set up is daisy chainable, would Fig. 3 be my
best bet and just install the terminator blocks on the Tape drive?
Ray Rankins |(518) 387-7340 | INTERNET: rankins@argentina.crd.ge.com
2 Moonglow Rd. |(518) 583-3320 | COMPUSERVE: 71131,3236
Gansevoort, NY 12831 | | AmericaOnline: RayRankins
<insert standard disclaimer here>esmith@goofy.apple.com (Eric Smith) (08/18/90)
In article <11143@crdgw1.crd.ge.com> rankins@argentina (raymond r rankins) writes: I am putting together a case with Quantum SCSI drive and a 3M tape drive in it. What is the best way to wire this up and terminate it? Someone recommended that the tape drive be at the end of the SCSI chain. Here is what I've come up with so far: ([] = 50 pin Centronics connector) SCSI in SCSI out [] [] [] [] [] \ / \____/\ \ \ _____ / \ _____ \ _____ \/ \/ \/ \ \/ \ _||_ _||_ _||_ _||_ _||_ _||_ | | | | OR... | | | | OR... | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |____| |____| |____| |____| |____| |____| Disk Tape Disk Tape Disk Tape Fig. 1 Fig. 2 Fig. 3 I believe someone posted in comp.periphs.scsi that Fig. 1 is the proper way that a case should be wired. If so, is it okay just to install the resistor packs directly on the tape drive to terminate the SCSI bus? Would I need any further termination like on the SCSI out connector in Fig. 1? Figure 1 is the correct way to wire it if you want daisy chaining capability. If you use this configuration but don't daisy chain anything from it, you need an external terminator. It is not a good idea to use the terminator packs on the tape drive with this configuration, as it is easy to forget to remove them when you want to daisy chain things. Fig. 2 doesn't seem at all right for a bus system like SCSI, but that's the cable set up that came with the case. Where would you place the terminators in a set up like that? Which connector should be the SCSI in, or doesn't it matter? Figure 2 is just plain wrong. Unfortunately this is how most devices are wired. If you use this, use the SCSI connector further from the drives, and use the termination pack on the tape drive. Don't use the other SCSI connector. If I don't care if the set up is daisy chainable, would Fig. 3 be my best bet and just install the terminator blocks on the Tape drive? Figure 3 is fine with the terminator on the tape drive. -- Eric L. Smith Opinions expressed herein do not necessarily reflect those esmith@apple.com of my employer, friends, family, computer, or even me! :-)
billsey@agora.uucp (Bill Seymour) (08/19/90)
In article <11143@crdgw1.crd.ge.com> rankins@argentina (raymond r rankins) writes:
:I am putting together a case with Quantum SCSI drive and a 3M tape drive
:in it. What is the best way to wire this up and terminate it? Someone
:recommended that the tape drive be at the end of the SCSI chain. Here is
:what I've come up with so far: ([] = 50 pin Centronics connector)
:
: SCSI in SCSI out
:
: [] [] [] [] []
: \ / \____/\ \
: \ _____ / \ _____ \ _____
: \/ \/ \/ \ \/ \
: _||_ _||_ _||_ _||_ _||_ _||_
: | | | | OR... | | | | OR... | | | |
: | | | | | | | | | | | |
: | | | | | | | | | | | |
: | | | | | | | | | | | |
: |____| |____| |____| |____| |____| |____|
:
: Disk Tape Disk Tape Disk Tape
:
: Fig. 1 Fig. 2 Fig. 3
:
:
:I believe someone posted in comp.periphs.scsi that Fig. 1 is the
:proper way that a case should be wired. If so, is it okay just to
:install the resistor packs directly on the tape drive to terminate the
:SCSI bus? Would I need any further termination like on the SCSI out
:connector in Fig. 1?
:
:Fig. 2 doesn't seem at all right for a bus system like SCSI, but
:that's the cable set up that came with the case. Where would you
:place the terminators in a set up like that? Which connector should
:be the SCSI in, or doesn't it matter?
:
:If I don't care if the set up is daisy chainable, would Fig. 3 be my
:best bet and just install the terminator blocks on the Tape drive?
Either Fig. 1 or Fig. 3 are correct. Fig. 1 is used when you need to
pass the SCSI bus onto other devices, or if you're using an external SCSI
termination pack. Fig. 3 is correct if this one end of the SCSI bus and
the tape drive has terminating resistors installed. Fig. 2 *can* be used
in replacement for Fig. 3, but only when you're not actually plugging
in anything in that second 50 pin connector. Again, the tape drive needs to
have terinating resistors installed.
Note that Fig. 1 shouldn't be used if it's the last device on the
bus and the terminating resistors are installed on the tape, instead of
in an external block plugged into that second 50 pin connector.
For your use, go ahead and leave it as it is... It'll work fine.
If you decide at some future time to add more peripherals, just use some
Fig. 1 types between your host adapter and this box.
:Ray Rankins |(518) 387-7340 | INTERNET: rankins@argentina.crd.ge.com
:2 Moonglow Rd. |(518) 583-3320 | COMPUSERVE: 71131,3236
:Gansevoort, NY 12831 | | AmericaOnline: RayRankins
:<insert standard disclaimer here>
--
-Bill Seymour ...tektronix!reed!percival!agora!billsey
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