20 Aug
2006
20 Aug
'06
7:08 a.m.
At 04:19 PM 8/18/06 -0400, you wrote:
37 pin. This was what was used for the external floppy drive port on the
original IBM PC.
> BTW the B
in DB refers to the size shell. The 25 pin connectors
> used on the original IBM are B size. Other sizes use a different
> letter ie DE, etc. But a lot of people call every size "DB"
Until relatively recently I was one of them. :-(
So what letters are used for other sizes?
DA is the 15-pin size, the one used by AUI Ethernet back in the heyday
of 10base5.
DB is the 25-pin size, the one that's standard for serial ports
(de-jure standard, not the 9-pin de-facto standard). Also used for
peecee parallel ports and older Macintosh SCSI, and doubtless a bunch
of other things too.
DC is a size I almost never see, and I don't remember the exact pin
count. 37? 39? Something like that.
DD is a much larger size, supporting 50 pins. Some of the older Sun
equipment uses this for SCSI, which is the only use I know it from.
DE is the small size, used with 9 pins for the serial connectors I
mentioned above and with 15 pins for peecee video ("VGA").
Good example. They're both DE size connectors but the 15 pin VGA
connector uses a different insert and is a high density connector. FWIW
ITT Cannon makes ALL kinds of different inserts and pins for the different
shell. I used to write requirements for military equipment including stuff
using the D series connectors and there are MILLIONs of combinations. The
last time that I looked the Cannon connector catalog was over 300 pages
long and it's crammed full of different parts. You can dozens of different
shells, dozens if not hundreds of different inserts and then all kinds of
different contacts including coaxial, high current and many specialty
contacts and on top of everything else there are many different types of
attaching hardware including slide locks, the wire clips, screws, jack
posts and more. EVERY piece of these connctors was ordered separately so
there are thousands of different ways that they can be assembled. That's
why naming a specific configuration is so confusing.
Joe
I don't know why the order makes so much sense for DA through DD and
then goes wonky for DE. I conjecture that when it was originally
planned, nobody expected it to be used for anything that small, so the
DE was tacked on as an afterthought. (I suppose they could have used
D@, but that would make sense only to geeks who know their ASCII. :)
I also don't know whether there are any other sizes with names. Other
sizes, though rare, do exist; for example, NeXT used a D-shell
connector of an odd size, with something like 19 pins, to drive their
greyscale video displays.
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