[geeks] NeXT soundbox

[Mouse]

>> If that's the connector from a slab or cube to the monitor (and
>> things connected to the monitor), it's actually not a DB shell.
>> [...]

> I'm actually not sure - I saw it called DB19 in a variety of places,
> so I went with it.

Fair enough.  It's an incorrect term, but it _is_ a _common_ incorrect
term.  Most of the D-sub connectors get called DB-something, even
though that is incorrect unless they're using one particular shell
size.  I was guilty of this myself until I learned enough about the
terminology to start getting it right.

The letter after D indicates the size of the shell.  The part after
that indicates the pin count (and sometimes more, as in the case of
13W3, which could perhaps more properly be called DB-13W3 - 10 ordinary
pins and 3 co-ax video signals in a DB shell).  More strictly, I think,
the number indicates _potential_ pin positions; I've seen plenty of
cables that have only a subset of the DB-25 pins actually present, but
I have never seen them called, for example, a DB-3 for a DB shell with
only three of the DB-25 complement of pins actually present.  (I don't
know whether the formal spec addresses that point.)

There are five standardized D-sub shell sizes I'm aware of (and
possibly more I'm not): DA is the non-compact 15-pin one, used for
peecee joystick/midi ports and AUI Ethernet (and doubtless others - I'd
be astonished if any of these weren't used for more than I'm aware of);
DB is the usual 25-pin one, used for standard serial ports (EIA RS-232C
actually specifies the connector) and peecee parallel ports; DC is the
37-pin size (I looked it up), used for almost nothing in my experience
(the only example I can think of offhand was on a multi-port I/O card
which had an octopus breakout cable to go from DC-37 to the various
connectors for the ports it provided); DD is a three-row size which
I've seen used for SCSI and IPI disks; DE is the small size used with 9
pins for peecee serial ports and with 15 pins (with tighter pin
spacing) for video (typically called "VGA" after an early piece of
hardware that used it).  Why the size increases until dropping back
down upon getting to DE I don't know; I speculate that the DE size was
an afterthought, tacked on after the DA through DD specs had already
been frozen.

I rarely see a D-sub of any other size.  When I first saw the NeXT
video connector, I had a bit of cognitive dissonance which I might
today put into words as something like "but, but, that's too long for a
DA and too short for a DB, how can that _be_??"  I still can't recall
seeing any D-sub size other than DA, DB, DC, DD, DE, and the 19-pin
size used by NeXT, though I'm sure examples must exist.

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