[COFF] 52-pin D-Sub?

[dave at horsfall.org (Dave Horsfall)]

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On Fri, 28 Feb 2020, Clem Cole wrote:

> DZ-11 sucked... for a number of reasons, the SW issue being just part of 
> them, but they were short pinned and really did not do modems well, 
> particularly high-speed ones like the Trailblazer.  As you said, you 
> could make them work, but why bother?

We used ours for local terminals only; 8 DZ-11s on the 11/70 worked fine 
(I don't recall how fast, but probably around 2400/4800).  As I said, it 
came down to the driver.

> Unix folks figure out the best idea was to use the Able DH/DM -  
> cheaper, only one unibus slot for 16 ports (as opposed to 2 for the DZ), 
> fully wired on the DB25 end, hardware flow control and just worked 
> better in that is will DMA.  What was not to love...

Sure, but then DEC Field Circus won't touch the box.

> FWIW:  One of the guys behind DZ (who I will leave nameless) also 
> screwed up the first serial port on the Masscomp MC/500 after he left 
> DEC. I got there too late to fix it in the first version of the CPU 
> board.  So it was not fixed until I tore him a new one and educated him 
> on how RS-232 actually worked (I was the first lead for the data com 
> group as well as 1/2 the OS team).  I never quite understood why HW 
> folks often though of the serial port as '3-wires' -- sigh.

Heh heh :-)  I don't think I've ever seen RS-232 used "properly" i.e. 
implementing DSR/DTR or RTS/CTS for other than flow control etc, and using 
the secondary pins as well.

-- Dave