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Re: Ultra 60 SCSI External Interface

Discussion in 'Sun Hardware' started by ChrisQ, Mar 22, 2009.

  1. ChrisQ

    ChrisQ Guest

    rkiesling wrote:
    > Hello, all,
    > I would like to find information about terminating an Ultra
    > 60's external SCSI interface. The system occasionally tries
    > to write and reset the SCSI device, and then times out with
    > a failure. I cannot find information in the Sun docs about
    > whether an external terminator is needed if there are no
    > devices attached to the port, or about the SCSI termination
    > on the mainboard, if that is only related to the internal
    > SCSI assembly. ISTM the external port should be
    > self-terminating, but I'm only guessing.
    >
    > On a related note, are there any opinions about which
    > outboard SCSI disks would be fast enough not to unduly slow
    > down the system (2 x 450 Mhz UltraSPARC, 1GB RAM) for disk
    > intensive tasks.
    >
    > TIA. Replies here or with an e-mail message, please.
    >


    If we are being pc here, scsi buses should always be terminated at both
    ends, though you can sometimes get away with no termination if the cable
    is very short, say around 1 foot. Termination at the controller end is
    handled by the controller. The early Sun external boxes (50 pin) nearly
    always needed a terminator on the 2nd connector, but the later 16 bit
    (68 pin) boxes have internal termination, though it doesn't break
    anything if you fit an external termination as well.

    While it depends on the cable length, number of boxes in the chain, I
    always fit a terminator just to make sure. The Sun badged boxes often
    have diagrams inside the lid describing allowed configurations, cable
    lengths etc and there's probably more on the Sun website...

    Regards,

    Chris
     
    ChrisQ, Mar 22, 2009
    #1
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  2. ChrisQ

    DoN. Nichols Guest

    On 2009-03-23, rkiesling <> wrote:
    > ChrisQ <> writes:
    >
    >> rkiesling wrote:
    >>> Hello, all, I would like to find information about terminating an
    >>> Ultra
    >>> 60's external SCSI interface. The system occasionally tries
    >>> to write and reset the SCSI device, and then times out with
    >>> a failure. I cannot find information in the Sun docs about
    >>> whether an external terminator is needed if there are no
    >>> devices attached to the port, or about the SCSI termination
    >>> on the mainboard, if that is only related to the internal
    >>> SCSI assembly. ISTM the external port should be
    >>> self-terminating, but I'm only guessing.


    [ ... ]

    >> While it depends on the cable length, number of boxes in the chain, I
    >> always fit a terminator just to make sure. The Sun badged boxes often
    >> have diagrams inside the lid describing allowed configurations, cable
    >> lengths etc and there's probably more on the Sun website...

    >
    > That sounds like a safe bet. I suppose I should try the
    > external termination as soon as I can.


    Who made the boxes which your external drives are in? If they
    are from Sun, *and* are 68-pin, they will automatically terminate the
    bus at the last box in the chain. Examples of these boxes are the
    UniPacks, the FlexiPacks (rather rare dual drive ones), and the
    MultiPacks, which can either hold 6 1.6" drives or 12 1" drives
    depending on the model. (The one for 1.6" drives can also hold 1"
    drives, but no more than 6 of either.)

    With these -- you *don't* need an external terminator.

    And -- if you do get an external terminator, make sure that it
    is the right kind. They are availalble as:

    1) SE (Single-Ended) terminators.

    2) HVD (High Voltage Differential) terminators.

    3) LVD (Low Voltage Differential) terminators.

    4) Auto switching between SE and LVD (LED color changes depending
    on which mode it is in.)

    The bus on the back of the Ultra-60 is SE (Single Ended), so
    look for either type (1) or type (4) above. HVD will not work at all,
    and I'm not sure about a plain LVD one.

    > This resetting doesn't affect the operation of the system,
    > I should note, except to print all of the notices of the
    > failed operations on the console.


    And to slow down the eventual transfer rate significantly.

    > But there isn't any information about the internal termination,


    The internal termination (for the computer end of the chain) is
    there, and you have no control over it. It is needed, and it is
    present -- end of game.

    The external end *must* be at the last drive box connector on
    the entire chain. Putting it closer will result in an unterminated stub
    on the SCSI bus.

    > nor about the auto-termination of the internal drives, so I might
    > assume, correctly or incorrectly, that the termination of
    > the internal bus is never meant to be an issue, and perhaps
    > the fault lies elsewhere - a scary thought.


    The termination of the internal drives is automatically present.
    Nothing to worry about -- and that is a different SCSI bus than the
    external one, so no problems.

    I actually can't go out to dig out one of my Ultra-60s to verify
    this because I am recovering from cataract surgery, and hav been told
    not to lift anything over 20 pounds. The drawing in the FEH (Field
    Engineer's Handbook) appears to show a larger connector to connect to the
    DVD drive, so I would guess that includes the terminator as part of it.
    But the drawing is small enough so I can't be sure.

    If you have external drives in non-Sun boxes, or in the older
    boxes with 50-pin connectors, then you may well need separate
    terminators. (For that matter -- look carefully at each connector.
    Once at work I encountered, on some brand new equipment, a SCSI cable
    which had the end pin at one end leaning against the next one -- and
    that broke out the partition between the two socket holes and tilted it,
    causing the next connector plugged into there to bend its pin -- and
    each other connector on the boxes into which they were plugged got their
    partitions broken out too, causing the problem to proliferate. I was
    able to tease the partitions back into place, and use some tiny
    needle-nose pliers to straighten the pins on all the connectors, so
    things started working again. But such a bent pin will cause the bus to
    get quite confused, and could indeed be your problem. (Also, a cable
    with a disconnected wire in it could cause similar problems, so try with
    other cables as well.

    Good Luck,
    DoN.

    --
    Email: <> | Voice (all times): (703) 938-4564
    (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
    --- Black Holes are where God is dividing by zero ---
     
    DoN. Nichols, Mar 24, 2009
    #2
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