Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!snorkelwacker!apple!goofy.apple.com!esmith From: esmith@goofy.apple.com (Eric Smith) Newsgroups: comp.periphs.scsi Subject: Re: Apple SCSI termination Message-ID: Date: 17 Aug 90 20:10:37 GMT References: <11143@crdgw1.crd.ge.com> Sender: usenet@Apple.COM Followup-To: comp.periphs.scsi Organization: Frobozz Magic Widget Company Lines: 56 In-reply-to: rankins@argentina's message of 17 Aug 90 17:36:13 GMT 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! :-)