SUMMARY: Minimum scsi length

Date: Mon Apr 26 1993 - 20:43:22 CDT

-------Original request ---------------------------------------------
Hello Sun gurus

    We have a sun 3/60 that has a external scsi shoebox attached to it.
    Inside the shoebox we have a esdi disk and a scsi to esdi controller.

    Also attached to the scsi ribbon cable we have a scsi qic tape drive
    and another scsi disk.

    Everything worked until one day when everything stopped working.

    After probing around the shoebox we noticed the outer wire of scsi
    ribbon cable was slightly broken. After making a new ribbon cable
    everything works except the one scsi disk drive which is in the middle
    of the internal scsi ribbon cable.

    The disk light flashes when I run the format command but the disk
    is not found in the list of disks. The disk is also not recognised
    on boot up.

    Is there a minimum length of scsi cable required between scsi devices?
    We do have scsi terminators on the last device.

    We are running sunos 4.1.1 on the sun3/60.

    Is there any other way of software testing scsi disks?

-------Original request ---------------------------------------------

We confirmed the scsi disk drives are dead.

Thanks to the following people who answered:

Summary of replies:
1. I recall a recent posting in comp.periphs.scsi mentioning that the
   minimum length is 0.33 metres.

2. Check to see total length < 9 feet. Seems to be the limit on Suns.

3. Check terminators. Make sure only the last device is terminated,
   or there is a terminating connctor in place.

4. You may wish to try a different cable. These ribbon cables are
   easy to break.

5. Another thing: do you have a double shoebox? Some of these are badly
   wired (Intertechnology in particular ...), with a Y configuration inside
   instead of a true loop. We have one of those; another got
   delivered and I had the tech come in and replace it with a proper
   internal ribbon cable. I believe they've got it right now ...

6. This experience you are having has happened to me also.
   My problem had the exact same symtoms as you indicate.
   This is what happened to me. When the middle connector
   was crimped on it did not align quite properly. I could
   see the drive being accessed via light but drive was
   not found. CAREFULLY reinstalling the connector solved
   the problem. Good luck.

7. Sounds like you may have a bad cable (I know its new), bad connector, or bad
   connector crimp. I would inspect the drive for bend pins, move the drive
   to another connector on the cable, and finally try changing the ID to that
   of another disk which *does* work (obviously disconnect the drive whose ID
   you steal). chances are there is nothing wrong with the drive!

Robert J Wolf, Sun System Admin. DCIEM, CFB Toronto PO Box 2000 1133 Sheppard Avenue West
uunet!!dciem!rwolf North York (Toronto), Ont., Canada M3M 3B9
Internet: Phone: (416)635-2073 FAX: (416)635-2104
"Capitalism with environmental ethics will benefit the entire world."

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