On Thu, 8 Jan 1998, Michael Sokolov wrote:

>    What I don't quite understand is why do they use unit plugs in the first
> place. SDI uses purely radial connections for multiple drives, and each
> drive connects to a different port on the controller. On all machines with
> RAxx disks that I have seen (only two really :-)), there was a perfect
> match between the number of the port on the controller and the number on
> the unit plug on the drive. Does anyone have a clue as to what's going on?

You obviously haven't seen enough hardware. :-)
If you ever connect a HSC, you'll see the point in having a unit number on
the disk, things will get hopeless very fast otherwise.
(A HSC is an intelligent disk controller for the CI-bus, and the more
modern ones can control up to 48 RA-disks...)
Also, each KDB-50 can only connect 4 drives. What if you'd like to have
more drives on your system? Should each be numbered 0-3, or should the
disks on the "second" controller be numbered 4-7, or what? Also, if you
moved the drive to another connected, do you really want it to
automatically get a new number? Accidents would be coming along real
quick, I'd say...

>    As for documentation, I have EK-0RA81-OM, the user's manual for RA81.
> Yes, that's for RA81, not RA82. RA81 is an older model, it holds only 450
> MB formatted. The two drives are very similar. The difference in capacity
> is probably due to a different number of platters or a different recording
> density. The mechanics (the HDA and the spindle motor) look identical, at
> least in external appearance. The logic boards look quite different,
> though.

The difference is in recording density...

>    One more caveat. These drives seem to be quite unreliable (I have one
> RA81 and one RA82, and both fault when I try to spin them up. Fixing them
> is what I have asked the DEC guy for the docs for.) So before you start
> thinking about what you are going to fill your vast disk space with, check
> whether the drives actually work. You don't need to have the VAX itself
> working for this test, just power up each drive and see if it spins up
> without faulting and comes up ready. It's best to do this test without
> connecting the drive to the VAX, but the interface enable button on the
> drive should be pushed in, or the ready light won't go on even if the drive
> is ready. Another caveat. When reading the front panel indicators, remember
> than they are not LEDs but small light bulbs, and they do burn out. I had
> to check/replace them on both of my drives before I could read the actual
> fault codes.

Much better to connect a terminal to the drive and talk with it. You can
run more diagnostics, get better error reporting and don't depend on lamps
that might be burned-out...
Both the RA81 and RA82 has a terminal connector inside it, if you open up
the back part.

Isn't this in the user manual???

>    Dave McGuire <mcguire@neurotica.com> wrote:
> > Incidentally, I don't see an
> > SDI disk controller in there anywhere...weird...
>    Well, if the VAX works, it must have either a KDB50 on the BI or a UDA50
> on the UNIBUS (the latter seems unlikely to me, although I don't know
> anything about the architecture of VAX 82xx, common sense suggests to me
> that if BI is its native bus and UNIBUS is not, the disk controller should
> be on the BI).

Sorry, but no. Most likely, it has been using a HSC-controller connected
to the CI-bus.
This also happens to be the preferred controller if you have a
VAX-cluster, since it means that all computers on the CI-bus can access
the drive directly.

It would be really nice to get a CI-driver to NetBSD. Anyone who have the
docs and the interest?

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt@update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol