On Mon, 28 May 2001, Gunther Schadow wrote:

> Hi,

> at each end. I can actually screw those on my CI bus connectors.
> >From what I heard, I imagined a CI cable being a big pipe of
> at least 1 inch diameter, was I wrong and I do have a CI cable?

There are two types of CI cable.  The old type was about 3/4 of an inch
in diameter and a real pain to deal with.  The new type was like 10b2
ethernet cable.  It has to be the right type of cable (just like you can't
substitute cable tv cable for 10b2 ethernet cable and get good results).

>
> I know I would need a star coupler to do anything useful with
> this, right?
>

The CI adapter will log errors without a star coupler at the minimum. This
question comes up frequently on comp.os.vms.  Check deja/google. I seem to
recall some types of CI adapters could be physically damaged without the
SC to make the electrical characteristics correct.


> However, I'm not eager to run an HCS as I don't really want to
> build a cluster around common storage. Instead, I was wondering
> about other uses of the CI bus. I heard it is pretty impressive in
> terms of throughput, so would be a waste if it ended up unused.

About like FW SCSI although more capable of operating at peak rated
performance.  The new HSJ80's get impressive performance by using multiple
CI cards and SC's.  There were neat features to reduce IO and CPU load
which even modern gizmo's like Fibrechannel have implemented imperfectly
if at all.  The CI cards know how to look through VMS page tables
independently of the CPU, and various commands for disk shadowing and
other operations could be performed by the intelligent RAID controllers
with minimal IO back to VMS. (and CI was supported on earlier versions of
Digital Unix on the big Alpha Turbolaser machines)

You can check the Compaq web pages for the (rather snotty) "OpenVMS Wizard"
whose archives has very accurate information on many of your questions
about CI.  Sorry I don't have the url handy but email me if you can't find
it.

> And since a 100-TP Ethernet card does not exit for VAXen, I wonder
> whether one could use a CI bus as a data link layer for IP? Not

Check google.  I recall stories of people running DECnet over CI in the
early days when ethernet was 10b2 and 10b5 and subject to problems when
people fiddle with the cables wrong.

> My CI interface has 4 connectors "A" and "B" for each
> input "->0" and output "0->". Will one connection to a star

These are two paths, transmit and receive.

> coupler use all four of those or only two? How absolutely
> certain is it that one cannot make a direct link between two
> machines without a star coupler?

All four, again check google for VMS stories about trying to operate
without a star coupler.