[Info-vax] SET TERM /TTSYNC on ancient VMS versions

[Johnny Billquist]

On 2018-08-15 22:38, hans.huebner at gmail.com wrote:
> Am Mittwoch, 15. August 2018 20:31:03 UTC+1 schrieb Stephen Hoffman:
>> If you turn off flow control, you'll get communications problems.
>> Overruns from host to terminal are more common, but there are folks
>> that could outrun the receive buffers on some configurations.  And
>> sometimes the host just isn't ready.  Sooner or later, there'll be
>> problems with input or output.  Loss, corruptions or whatnot.
> 
> In-band flow control was always a pain in the rear.  Of course, it was also a cheap solution to a problem.  Better async multiplexers and terminal servers, however, had full modem control, and the VMS terminal driver supports out-of-band flow control at least in VMS V5.x.  I would like to know whether hardware flow control was added in V5.x or earlier.  This is out of historic curiosity.

Well, first of all, using modem controls for flow control is an abuse of 
the signals. They were never intended for this. And so DEC did, 
correctly, not use the signals that way.

I'm surprised to hear that DEC did have hardware flow control back 
already in VMS V5. Are you sure about that?

I know that on the PDP-11 side, there is no support for hardware flow 
control to this day.

And on the terminal side, it took quite a while before DEC grudgingly 
added the capability. Can't remember if the VT300 series has it, but it 
might not have been until the VT400 series.

In-band flow control certainly have some issues, but they are almost 
always just related to programs who want to pass all characters through 
cleanly. Apart from that, it works just fine.

And if people wanted all characters on a terminal, it can be done 
reliably without flow control as well. Emacs is an example of that. But 
it do require that the program then have quite some intimate 
understanding of the hardware involved.

   Johnny

-- 
Johnny Billquist                  || "I'm on a bus
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email: bqt at softjar.se             ||  Reading murder books
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