baumgart@esquire.dpw.com (Steve Baumgarten) (07/12/90)
In article <42859@apple.Apple.COM>, blob@Apple (Brian Bechtel) writes: >>Apple is woefully negligent in this area; although the IIfx comes with >>"Technical Info" and "Setting up Your IIfx" manuals, neither of them >>address the question. > >I disagree. Appendix A of "Setting up Your IIfx" contains complete >instructions on termination. Well, something's missing from mine then, because I'm sitting here with that very manual in my hands and there's no Appendix A. I can't find a discussion of IIfx-specific SCSI termination anywhere in the manuals I got with my Mac. I got two booklets (the Technical Info and Setting Up manuals mentioned above), plus the Reference guide (which does contain some explanation about SCSI termination in general, but doesn't go into IIfx specifics). >If you have an internal drive from Apple, it's already terminated. >Don't add any additional termination. If the drive is by some other >company, contact that company for termination information. You do need >special termination; see Technical Note 273 for much more detail. > >The basics of SCSI termination are: > * One terminator at the beginning of the chain > * One terminator at the end of the chain > * No terminators anywhere else. >With that in mind, put the black terminator that came with the IIfx on >the last device in the SCSI chain. You can put the terminator either >in-line with the last cable, or on the adjacent connector. > >--Brian Bechtel blob@apple.com "My opinions, not Apple's" Right, that much I've finally got figured out. I should have been more specific in my original posting: I have a Wren 630 MB internal drive (either a Wren VI or VII) that does not, as far as I know, have any termination, and an external tape drive that isn't terminated either. My question, then, is whether or not to use that T-extender; in the email responses I got, people seemed to be of two minds... here are some excerpts: From: dplatt@coherent.com (Dave Platt) Date: Tue, 10 Jul 90 11:55:08 PDT To: baumgart@esquire.dpw.com Subject: SCSI termination on the IIfx 1. With only an internal drive. The internal hard drive (assuming it's an Apple drive) should be shipped with an internal terminator in place, and (assuming it's of a recent vintage) with the necessary termination-filter built into the drive. If the drive is a non-Apple drive, you should use it with its supplied internal terminator, and with the internal filter (the little extender-like thing). 2. With both an internal drive and an external tape drive. The internal drive should be configured as in (1). The external drive should use the Apple-supplied black external terminator. If the external tape drive has termination resistors on its board (many do), these should be removed. -- Date: Tue, 10 Jul 90 12:08:16 -0700 From: steph@cs.ucla.edu (Stephen Sakamoto) To: baumgart@esquire.dpw.com Subject: Re: IIfx SCSI termination question Organization: UCLA Computer Science Department Okay, heres the story on terminators. The MacIIfx comes with two terminators, an internal gray one and the external black one. This is how you use them: With an internal drive you don't use any of the special ones just the internal terminators on the drive. With an internal and external drives(s) you need to remove the internal terminators on the external devices. You then use the black terminator on the last external device. With no internal drive, but, external drive(s) you again remove any internal terminors on external drives. Use the black terminator on the last external drive and use the special gray terminator in the SCSI connector in the MacII. Let me know if you have any questions. Stephen Sakamoto UCLA Computer Science Department steph@cs.ucla.edu -- So the question is whether or not to use the extender. I've tried it both ways and had problems using the extender -- the hard disk seemed to go out to lunch after a while (though things were fine for about 10 minutes). Removing the extender worked fine. I guess since it's all working the way it is (no internal extender, using the black terminator on my tape drive), I should just leave it be. But I wondered whether although it's working it might be suffering a performance hit. Also, it seemed like there just should be some "right" answer to all this, and I have trouble going the "it works so don't mess with it route" in general. In any case, thank you to everyone who responded. I may play around with it some more, but if anyone is *sure* of the correct answer (especially someone from Apple), or knows why using the internal T-extender in my case would cause problems, please post or email and I'll try to follow through on any suggestions I receive. Thanks again for your help, everyone. -- Steve Baumgarten | "New York... when civilization falls apart, Davis Polk & Wardwell | remember, we were way ahead of you." baumgart@esquire.dpw.com | cmcl2!esquire!baumgart | - David Letterman