25 Oct
2012
25 Oct
'12
2:45 p.m.
On Thu, 25 Oct 2012, Pete Turnbull wrote:
On 25/10/2012 02:08, Tothwolf wrote:
Well, my point was that Cisco likely didn't "steal" the idea from Dave
Yost per se. Given that the pinout for the inside 6 connections of the
6P6C MMJ cables (DTR, TD, GND, GND, RD, DSR) is identical to that of the
Yost standard (RTS, DTR, TD, GND, GND, RD, DSR+CD, CTS) I suspect Dave had
some prior experience with the DEC 6P6C MMJ standard and used that as the
basis for the Yost 8P8C standard. The upside to this is that in a pinch,
you could take a 6P6C MMJ to 6P6C cable like those I used to make and plug
the non-MMJ end into an 8P8C connector and only lose RTS/CTS. [Note that
doing this with cheaper 6P6C plugs that don't have slots molded in for
pins 1 and 8 /will/ bend and damage pins 1 and 8 in the 8P8C connector, so
even though there are people who swear by using 8P8C jacks with 6P6C plugs
for stuff like POTS telephone applications, I don't really recommend it.]
Not so fast. DEC was already doing this with 6P6C
MMJ cables with a
nearly identical system before Dave Yost came up with his standard
using 8P8C adapters and cables. The additional two wires available with
the 8P8C connectors allows for RTS/CTS.
Yes, I know - I have plenty of MMJ stuff - but it was always
DEC-specific. The beauty of the Yost pinout is that it is uses
ubiquitous cables as well as a simple and versatile pinout. Hence it's
adoption by Cisco and Sun. Everyone else was doing something unique and
often not even consistent within one product line (three different 8P8C
pinouts for Shiva terminal servers with the same model number is the
most extreme example I recall). The Wikipedia page lists three 8P8C pinouts. My
department's internal
wiki lists eight that we had to have cables for :-( Well, seven we
used, and TIA561 for completeness. I've never known anything actually
use that one.
Are any of those other pinouts "standard"? I've found the material in
several of these Wikipedia articles to be very incomplete. That table in
particular only gives the pinout for the DCE version of the Yost standard,
and doesn't even label it as such. I'm tempted to update it, but the table
format someone used doesn't lend itself to easy updates and it has been
over a year or more since I worked with these sorts of tables and
converted one to the easier to manage format. Sigh.