Re: SCSI scanner not recognized -- SOLUTION - Mandriva

This is a discussion on Re: SCSI scanner not recognized -- SOLUTION - Mandriva ; > David W. Hodgins wrote: > > You haven't said if you've checked termination. > > Neither the CDROM nor the tape drive were terminated on the > internal ultra/SE connector on my Adaptec 19160B Ultra160 SCSI > adapter. Both ...

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Thread: Re: SCSI scanner not recognized -- SOLUTION

  1. Re: SCSI scanner not recognized -- SOLUTION

    > David W. Hodgins wrote:
    > > You haven't said if you've checked termination.

    >
    > Neither the CDROM nor the tape drive were terminated on the
    > internal ultra/SE connector on my Adaptec 19160B Ultra160 SCSI
    > adapter. Both of these units are on the same 50-pin ribbon cable
    > and have IDC50 connectors. See here for good SCSI connector
    > pictures: http://www.ramelectronics.net/html/scsi_connecters.html
    >
    > The SCSI hard drive is terminated on the 68-pin LVD internal
    > connector. It works fine.
    >
    > The UMAX Astra 1220S scanner has a termination on one of its two
    > DB25 SCSI-1 connectors. The scanner connector connects to the
    > Adaptec 50-pin HD50 external connector.
    >
    > For some reason the exact same device setup works on my Mandrake
    > 9.0 system with a BusLogic SCSI card.
    >
    > With bad terminations on the Adaptec's internal 50-pin connector,
    > then the scanner on the external 50-pin connector isn't
    > recognized, nor is the hard drive on the internal 68-pin
    > connector. But, both the CDROM and tape drive on the internal
    > 50-pin connector are recognized, and both of them are functional,
    > even with the bad termination.
    >
    > By disconnecting the 50-pin cable from the Adaptec's internal
    > connector, then the scanner and the hard drive work just fine.
    > Obviously the CDROM and tape drive don't work.
    >
    > > The internel cable must be terminated at the end of the cable,
    > > either by a device that provides termination, or by actual
    > > terminating resistors.

    >
    > 68-pin cable is terminated. 50-pin internal cable is
    > unterminated.


    I bought 50-pin internal terminators. Now everything is
    terminated, and all devices are recognized and working. I'm
    quite happy. But, I'm still a little confused about why the same
    SCSI setup, without 50-pin internal termination, worked on a
    previous version of Mandrake and an old ISA BusLogic SCSI card.
    That'll have to remain a mystery.

    Cheers...

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  2. Re: SCSI scanner not recognized -- SOLUTION

    Kevin the Drummer wrote:

    > But, I'm still a little confused about why the same
    > SCSI setup, without 50-pin internal termination, worked on a
    > previous version of Mandrake and an old ISA BusLogic SCSI card.


    You have been enlightened by the magic of SCSI. Now repeat the mantra, "have
    you checked the termination?"

  3. Re: SCSI scanner not recognized -- SOLUTION

    On Mon, 20 Aug 2007 11:26:02 -0400, Kevin the Drummer wrote:

    > I bought 50-pin internal terminators. Now everything is
    > terminated, and all devices are recognized and working. I'm
    > quite happy. But, I'm still a little confused about why the same
    > SCSI setup, without 50-pin internal termination, worked on a
    > previous version of Mandrake and an old ISA BusLogic SCSI card.
    > That'll have to remain a mystery.


    Different card, different results. The point is, that scsi systems
    must have termination at both ends of the chain. If there is only
    one cable, then the termination must be on the host adapter, and
    the last physical device on the cable, or the end of the cable.

    If there are two cables, the ends of both cables must be terminated,
    either by devices, or resistors. The host adaptor, in this case,
    must not be terminated. The chain must be terminated at both ends,
    and nowhere in between.

    Inproper termination may work, some of the time, but is unpredictable.
    If it does work, say 99% of the time, that 1% will be very difficult
    to track down to the termination problems. The first signs of improper
    termination will often be data corruption, or devices some times not
    being visible, on the bus.

    With scsi, always check the termination, on installation, or whenever
    adding/removing/moving devices.

    See http://searchwincomputing.techtarget...152257,00.html
    for some more info, and links.

    Regards, Dave Hodgins

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  4. Re: SCSI scanner not recognized -- SOLUTION

    David W. Hodgins wrote:
    >
    > Inproper termination may work, some of the time, but is unpredictable.
    > If it does work, say 99% of the time, that 1% will be very difficult
    > to track down to the termination problems. The first signs of improper
    > termination will often be data corruption, or devices some times not
    > being visible, on the bus.


    The big surprise for me here is that I managed to run the
    BusLogic card and the two SCSI devices in question on it's 50-pin
    internal bus for just over 11 years, without any sign that
    anything was wrong.

    I do know most of the rules for addresses, terminations, etc. I
    just didn't think to check something that had worked for so long.
    That's the real lesson for me -- check the stuff that's "known to
    be working" to see if it's broken. For me, the answer was that it
    really was broken.

    > With SCSI, always check the termination, on installation, or whenever
    > adding/removing/moving devices.
    >
    > See http://searchwincomputing.techtarget...152257,00.html
    > for some more info, and links.



    --
    PLEASE post a SUMMARY of the answer(s) to your question(s)!
    Show Windows & Gates to the exit door.
    Unless otherwise noted, the statements herein reflect my personal
    opinions and not those of any organization with which I may be affiliated.

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