baumgart@esquire.dpw.com (Steve Baumgarten) (07/10/90)
I know people keep asking this with alarming regularity, but does anyone know the correct way to terminate the SCSI chain in a IIfx: 1. With only an internal drive. 2. With both an internal drive and an external tape drive. 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. They do, however, enclose a single slip of paper that helpfully states "The SCSI chain should always be properly terminated," or something equally inane. Basically, I know I'm supposed to use the special black-plastic external terminator if I have any external SCSI devices. But I've also heard that the gray-plastic T-shaped doohicky that looks like an extender is, in fact, an internal terminator and should be used -- at least in some cases. Please either post or respond by email; I'll summarize to this group once I finally get this all straightened out. And if you do reply, you can faithfully assume that I know absolutely nothing about any of this -- don't worry about explaining things at a very basic level. Thanks in advance for your help. -- 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
blob@Apple.COM (Brian Bechtel) (07/11/90)
baumgart@esquire.dpw.com (Steve Baumgarten) writes: >I know people keep asking this with alarming regularity, but does >anyone know the correct way to terminate the SCSI chain in a IIfx: > 1. With only an internal drive. > 2. With both an internal drive and an external tape drive. >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. 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"
davism@creatures.cs.vt.edu (Mat Davis) (07/12/90)
In article <42859@apple.Apple.COM> blob@Apple.COM (Brian Bechtel) writes: > >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. > >--Brian Bechtel blob@apple.com "My opinions, not Apple's" But the manuals that came with a CMS drive state that you *shouldn't* use termination on a two-drive chain *if* the cable is less that two feet long. From what I've seen/heard about SCSI termination and some of the problems I've had, I'm about to decide that you just have to experiment with different setups to get everything "just right". And while I'm at it, is there any software out there that can help diagnose SCSI problems? Right now I'm helping someone who's getting lots of SCSI error messages from A/UX, and unless the external Apple 80SC or the Apple tape drive is internally terminated, I *know* that it follows the rules above. Yet we're still getting "SCSI Protocol Error", "SCSI Sense Error", and lots of retries on the system. BTW, the setup is: IIci w/ 80M <-> External Apple 80SC <-> Rodime 210e (term. removed) <-> Apple tape drive, and only the tape drive has a terminator on it. Mat Davis Virginia Tech Computer Science Dept. (davism@vtopus)