[Simh] Simh Digest, Vol 158, Issue 14

[Clem Cole]

On Thu, Mar 9, 2017 at 2:16 PM, William Pechter <pechter at gmail.com> wrote:

> I did  Field  Service through 8650s and never saw them.  DMF32s - IIRC had
> modem control capability on some lines or is my memory shot.


​DMF32 and DZ had >>partial<< modem control.  It was crock in both cases
and did not work very well, which is why UNIX folks had to use the Able
boards to run Trailblazers or any other high speed modem.

The problem was the flow control was assumed to be in SW (^S/^Q) which
fails if you are running an 8 bit protocol like UUCP.  So you need full HW
modem control with RTS/CTS supported.   DZ's and DMF's supported DTR and CD
but lacked most of the others.


The other issue is that early UARTs had very shallow input buffers.   The
chips that were used in the DZ and DMZ over flowed out high data rates if
there was lots of interrupts.   Again - if you were running something like
a trailblazer modem or the like, where the modem the port connection was at
19.2K or higher, the dropped characters.

Clem
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