Re: Ultra 60 SCSI External Interface

"DoN. Nichols" <dnichols@xxxxxxxxxxx> writes:

On 2009-03-23, rkiesling <ctalk@xxxxxxxxxxxxx> wrote:
ChrisQ <blackhole@xxxxxxxxxxx> 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.

Thanks for the insight. I'm almost certain the problem
is somewhere other than the internal SCSI bus, but I'll have
to get back to it.

--
http://www.ctalklang.org

.

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