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Thread: 2nd IBM Hard Disk Question

  1. #1

    Default 2nd IBM Hard Disk Question

    Hi All

    The Rev 3 IBM/Xebec card that has been eluding me finally arrived today. I have it installed and have a single drive connected to it with the terminator and shunt block installed.

    I want to add a second identical drive. I've read on -0 degrees that I am to remove the terminator from drive 0, make sure it is in drive 1, and then change the shunt block on drive 1 to the 2nd drive, but how can I do that using the shunt that IBM provided on the drive already since my second drive came from a single drive system?

    Thanks,
    Daniel
    Daniel P. Cayea - The Lyon Mountain Company - Plattsburgh, New York 12901
    Vintage Equipment: IBM 5150 * IBM 5161 * ThinkPad 770ED
    Modern Equipment: MacBook Pro 13 * Alienware M15R3

  2. #2

    Default

    I was experimenting and leaving both drives terminators installed and drive select shunts on drive 1; the controller now detects both drives. Go figure.
    Daniel P. Cayea - The Lyon Mountain Company - Plattsburgh, New York 12901
    Vintage Equipment: IBM 5150 * IBM 5161 * ThinkPad 770ED
    Modern Equipment: MacBook Pro 13 * Alienware M15R3

  3. #3
    Join Date
    May 2006
    Location
    Melbourne, Australia
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    6,228

    Default

    Quote Originally Posted by lyonadmiral View Post
    I want to add a second identical drive. I've read on -0 degrees ...
    The diagram that you have pointed to is only part of the story. The full story is at [here], where there are multiple options.

    Quote Originally Posted by lyonadmiral View Post
    ... that I am to remove the terminator from drive 0, make sure it is in drive 1, ...
    Terminator on the drive that is at the end of the cable, and no terminator on the drive in the middle of the cable.

    Quote Originally Posted by lyonadmiral View Post
    ... and then change the shunt block on drive 1 to the 2nd drive, but how can I do that using the shunt that IBM provided on the drive already since my second drive came from a single drive system?
    By using 'OPTION #2: Twisted control cable' at the web page I pointed to earlier.

    Note that your terminology is confusing. Your, "to the 2nd drive", is better worded as "to the second drive-select position".

    Quote Originally Posted by lyonadmiral View Post
    I was experimenting and leaving both drives terminators installed and drive select shunts on drive 1; the controller now detects both drives. Go figure.
    I am figuring that you moved to a twisted cable.

    Because these cables are relatively short, one can normally get away with having the terminator on the drive in the middle of the cable, and no terminator at the end of the cable. But I think two terminators is asking for trouble (e.g. perhaps intermittent failing operations).

  4. #4

    Default

    I didn't take the cable out of the expansion unit and completely flatten it out, it's the stock cable that came with the unit with the Rev A Controller and the 10 meg drive; I replaced the controller with a Rev C and the single 10 meg drive with 2, 20 meg drives. The configuration that is working is both drives have terminators installed and the drive select shunts are set for single drive configuration. Advanced Diagnostics detects both drives, can low level format, and test each of them. If I removed the terminator from drive 0 (middle on the cable) and set the drive select shunt on the second drive (end of cable); advanced diagnostics detects only 1 drive but then can't format the drive and all tests fail. I've read all that -0 has written about cabling and drives, etc, I just find it peculiar on my setup, that it works in a configuration that is not documented, but doesn't work if its configured according to the docs.
    Daniel P. Cayea - The Lyon Mountain Company - Plattsburgh, New York 12901
    Vintage Equipment: IBM 5150 * IBM 5161 * ThinkPad 770ED
    Modern Equipment: MacBook Pro 13 * Alienware M15R3

  5. #5
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,228

    Default

    Quote Originally Posted by lyonadmiral View Post
    ... that it works in a configuration that is not documented, ...
    The minuszerodegrees.net page for the IBM/Xebec controllers does not show all workable configurations. It shows the common configurations. For example, you indicate that you have placed (physical) hard drive 0 in the middle of the cable. That's workable for the subject.

    A summary of what I consider to be the norm is at [here]. Per that, irrespective of whether a 'flat' or 'twisted' cable is being used, you get one drive, physical drive 0, up and running at the end of the cable. Then you add the second drive, physical drive 1, in the middle of the cable, without having to 'touch' physical drive 0 in any way.

    Quote Originally Posted by lyonadmiral View Post
    ... I just find it peculiar on my setup, .... , but doesn't work if its configured according to the docs.
    Which suggests to me that either that your configuration is not as you think it is, or you have faulty hardware.

    For example, the fact that you cannot get your configuration to work if there is only one terminator, might be due to: faulty terminator, wrong terminator type, terminator orientated incorrectly, faulty drive.

    For example, maybe you should well-examine the control cable to determine whether it is 'flat' or 'twisted'. I do that kind of stuff, just to remove assumptions from my 'equations'. Even reasonable or good assumptions are still in the end, assumptions.

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