[Simh] pdp11 - console input with high bit set

[Paul Koning]

> On Jul 24, 2020, at 2:28 PM, David Gesswein <djg at pdp8online.com> wrote:
> 
> On Fri, Jul 24, 2020 at 06:12:17PM +0000, Paul Moore wrote:
>> Not helped by not knowing what KSR really means.
>> 
> 
> Keyboard send receive. A model 33 teletype without paper tape.
> ASR was the model with paper tape, Automatic send receive.
> 
> DEC used teletype's that generated mark parity. From the manuals keyboards were
> available to generate other parity. A reasonable amount of old code for
> PDP-8's assumed mark parity. Later code ignores the upper bit.
> 
> I thought the high bit setting would be turned off if you used set tti 7b or
> 8b but never verified.

7b, yes.  But that only helps with software that sets the top bit on output, as some old Unices do.  It doesn't help with the problem Paul M raised, which is software that insists on mark parity input.

The right answer would be a tweak to the console emulation in SIMH pdp11.  I wonder if this was done for PDP8 and not PDP11 because it was known to be needed on the one but people hadn't run into it for the other.

	paul