[Simh] VAX DZ terminal controller unit?

Gary Lee Phillips tivo.overo at gmail.com
Fri May 20 14:38:10 EDT 2011


On Fri, May 20, 2011 at 1:20 PM, Phil Mendelsohn <phil at rephil.org> wrote:
> On 11-05-20 01:11 PM, Gary Lee Phillips wrote:
>
> This smells like the right area to be poking around in, but I seem to recall
> an awful lot of VTs that were wired just TX, RX, and ground and they just
> worked.  The handshaking lines were never sufficient and often not even
> necessary to make things play nice, IIRC.
>
If I remember correctly, you had the usual configuration options on
the terminal port. That means if you told the VAX (or the DZ) to
ignore hardware handshaking and use only XON/XOFF, it would do so.
Serial connections were the rule rather than the exception back in the
70s and 80s, so I'm sure it worked as specified back then with the
real hardware.

The only terminals we ever had attached to serial ports on our VAXen
were the operator consoles, though. The programmer and user terminals
were several floors away and used short serial links to a terminal
server that then connected to the hosts using LAT over a thick
Ethernet backbone.

At home I do have a real VT220 and an Alpha workstation. The VT220 is
connected to a serial port on the Alpha and operates as a console and
a user terminal, but I'm using a cable with all the handshake signals
intact. It works well enough.

I can also use that to telnet to the virtual VAX running on a separate
Linux box, and it operates as a proper VT220 there. Fun and great for
nostalgia, but pretty cumbersome to boot another computer up just to
use it as a character cell terminal. The Alpha and its disk tower use
a fair amount of extra electricity, too.

At work I also have an Alpha running, but it has been pressed into
"temporary" service as a proxy server (temporary now starting to look
indefinite after 7 months) and even though I own that hardware myself,
I can't easily mess with it for my own purposes right now. Hence the
current sticking point with DZ, since I'm running both Linux and SIMH
on my desktop workstation. I could (can, I've tested) ssh to the
Alpha, which is also running Linux now rather than OpenVMS, and then
telnet back to the emulated VAX, but something else that worked more
elegantly within the desktop PC itself would certainly be preferable.
;p

--Gary


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