Cooper wrote:
> 
> SDI is a funky balanced-serial, phase-encoded horror. It was designed
> that way so that there would be no charge buildup at either end. I

Why would anybody do such a thing?   Was this just an experiment in
twisted design or was there a good reason?

> recall it had a four-wire connector (the cables looked like liquorice
> straps, ie  quite wide and rectangular in cross-section, and of course
> black in colour).

There are 4 coaxial leads in an SDI cable.  There are multiple types of
cables.  First there is the cable going from one connector on the KDA50
and branching out to 4 male SDI plugs that get mounted on a bulkhead on
the host system.   Then there's the thick black female to female cable
to that goes between those connectors and the connector on the drive
cabinet.  Then there are the thinner white male to female cables that go
from the connection on the drive housing to the drive itself.  To make
things more confusing, cables swap pins so you must have an even or odd
number of cables, depending on the drive.  They must have been trying to
confuse people when thy designed this.
BTW.  For the RA90, use 1 black and 1 white cable between the bulkhead
on the system and the drive itself.

> I seem to remember it had a bandwidth of maybe four megabytes per
> second.

The data transfer rate seems pretty good on an RA90.  The access time
probably sucks compared to smaller drives.  

-- 
|  Boris Gjenero <bgjenero@undergrad.math.uwaterloo.ca>              |
|  Home page:  http://www.undergrad.math.uwaterloo.ca/~bgjenero/     |
|  "Luke, you're going to find that many of the truths we cling to   |
|  depend greatly on our own point of view." - Obi-Wan Kenobi, ROTJ  |