7 Replies Latest reply: Oct 20, 2005 9:32 PM by Allan Jones
Michael Hetes Level 1 Level 1 (55 points)
This is driving me nuts, largely because there hasn't been a SCSI-related problem here before. Particulars: Beige G3/266, 192MB RAM, OS 9.1, five true SCSI devices, split between internal and external buses.

Recently I removed a SCSI hard disk from the G3's internal SCSI chain. Prior to that (internally) it had both 8.4GB ATA and 4GB SCSI hard disks as well as a 12-speed SCSI CD-ROM. Since that change the internal CD-ROM will not show up unless all devices are powered up, which had never been the case before removal of the internal hard drive. According to the Apple System Profiler the driver for device #3 will no longer be available if only the external Jaz and Zip drives are powered up, but will miraculously return if all devices are. (I have screen shots of the System Profiler's results, both before and after, if anyone wishes to see these results.)

The SCSI externals consist of a Zip 100, a Jaz 1GB, a 2GB hard disk and a Sony Spressa CD-burner. All SCSI addresses are as follows:

Internal (ATA) HD = ID 0, fixed
External Jaz 1GB = ID 1
External HD 2GB = ID 2
Internal CD-ROM = ID 3, fixed
External Zip 100 = ID 5
External CD-burner = ID 6
Internal Mac CPU = ID 7, fixed

The cabling order for the above devices is as follows:

Internal (ATA) HD = Internal IDE cable
Internal CD-ROM = Internal SCSI cable
1. External HD 2GB (ID 2) =>
2. External CD-burner (ID 6) =>
3. External Zip 100 (ID 5) =>
4. External Jaz 1GB (ID 1) =>

Any thoughts/suggestions you folks might have for this arrangement would be appreciated.
  • Bill W Level 5 Level 5 (4,755 points)
    The first thing I'd try is a PRAM reset and then a CUDA reset. Since you've made hardware changes, maybe your mac's confused.
  • Michael Hetes Level 1 Level 1 (55 points)
    Thought I'd follow-up with my actions to this point:

    1. PRAM reset
    2. OS 9.1 Clean install
    3. CUDA reset

    None of the actions listed above seem to be the magic bullet. In fact it may have gotten worse; the latest System Profiler check showed that, when only the external Zip and Jaz drives are active, SCSI ID 3 no longer registers at all! And, unlike before, everything doesn't return to normal when all SCSI devices are powered up.The driver for SCSI ID 3 appears to be AWOL.

    (Does Apple allow PICTs or JPEGs to be posted along with one's questions on this site?)

    I'm stumped.
  • Bill W Level 5 Level 5 (4,755 points)
    Was the removed HD providing termination to the internal bus? Maybe you need to terminate the CDRom.
  • Michael Hetes Level 1 Level 1 (55 points)
    Terminating the internal bus was already taken into account. Sorry not to have mentioned this earlier.
  • Michael Hetes Level 1 Level 1 (55 points)
    Well, the issue has been solved. Going by my instincts, the devices were both readdressed and reordered. The SCSI addresses were changed according to a "frequency of use" factor. Cable arrangement was adjusted to more closely reflect the address order. Perhaps to an old pro this would appear to be common sense. It had just never been an issue with my equipment before.

    The new addresses, for the curious, are as follows:

    Internal (ATA) HD = ID 0, fixed
    External Jaz 1GB = ID 1
    Internal CD-ROM = ID 3, fixed
    External CD-burner = ID 4
    External Zip 100 = ID 5
    External HD 2GB = ID 6
    Internal Mac CPU = ID 7, fixed

    The cabling order for the above devices are as follows:

    Internal (ATA) HD = Internal IDE cable
    Internal CD-ROM = Internal SCSI cable
    1. External Jaz 1GB (ID 1)=>
    2. External Zip 100 (ID 5) =>
    3. External CD burner (ID 4) =>
    4. External HD 2GB (ID 6) =>

    There . . done!
  • Bill W Level 5 Level 5 (4,755 points)
    SCSI IDs and cable order aren't supposed to matter as long as you don't duplicate an ID number. But if it worked, declare a victory and move on.
  • Allan Jones Level 7 Level 7 (33,000 points)
    Glad it's solved. I had fits with the external SCSI chain on a Beige G3 at work (ZIP 100, JAZ, and scanner). All the gear arrived at the same time and I assembled stuff using cables shipped with the peripherals. The set-up required the use of an adaptor (25-50 pin or 50-25 pin --can't remember now) furnished with the JAZ to accomplish. It connected to the external SCSI port, so was the first widget in the physical chain. The chain was intermittent in function for months.

    Although the chain was within prescribed lengths between devices, I decided to order all-new cabling. I found off-the-shelf cabling of the exact lengths I needed, shortening the chain by a couple of feet. I also ordered the first run of cable so I did not have to use the adaptor on the computer's port.

    BINGO! The problem turned out to be the adapter. The first piece of original cable was a long and heavy SCSI-2 critter going to the JAZ. It weighed enough to pull down on the port and cause a few pins to make intermittent contact. The adaptor had clips, not screws, for securing to the computer and the whole mess was simply not up to the task.

    The new rigging without the need for adaptors never gave another hint of problems.

    AJ