Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!ogicse!intelhf!agora!billsey From: billsey@agora.uucp (Bill Seymour) Newsgroups: comp.periphs.scsi Subject: Re: Apple SCSI termination Message-ID: <1990Aug18.190937.1520@agora.uucp> Date: 18 Aug 90 19:09:37 GMT References: <11143@crdgw1.crd.ge.com> Organization: Open Communication Forum Lines: 63 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 : -- -Bill Seymour ...tektronix!reed!percival!agora!billsey ============================================================================= Bejed, Inc. NES, Inc. Northwest Amiga Group At Home Sometimes (503) 281-8153 (503) 246-9311 (503) 656-7393 BBS (503) 640-0842