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Re: PDP-8 ASCII question

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On Mon, 04 Apr 2016 16:15:38 +0200, Morten Reistad wrote:

> In article <dmf3pdFs66uU6@mid.individual.net>,
> Bob Eager  <news0006@eager.cx> wrote:
>>On Mon, 04 Apr 2016 13:01:50 +0200, Morten Reistad wrote:
>>
>>> In article <pfp9tc-bvt.ln1@news.informatik.uni-stuttgart.de>,
>>> Christian Corti  <cc@corti-net.de> wrote:
>>>>Dylan McNamee <dylan.mcnamee@gmail.com> wrote:
>>>>> That is a great thread - thanks for the pointer! It seems that this
>>>>> is mostly an artifact of papertape and 6-bit ASCII, both
>>>>of which (mostly) went away after the PDP-8.
>>>>
>>>>No and no.
>>>>First, ASCII is seven bits (octal 0-177). Second, it has nothing to do
>>>>with papertape or Teletypes. DEC simply defined the parity bit to be
>>>>mark (i.e. always 1), since the serial interface is 8 bits fixed.
>>> 
>>> They were not alone in doing this. Prime computer also had the MSB set
>>> in all of their ASCII. Saving a few cents worth of hardware in the
>>> serial ports and/or some cycles processing them. But leading to
>>> decades of incompatibility.
>>
>>ISTR having the same thing on a Honeywell DDP-516.
> 
> ISTR that the earliest Primes (up to the 400, ISTR) were
> embrace-and-extend versions of the DDP-5xx architecture. Later versions
> had compatibility-mode (R-mode?) that ran DDP-516 code.
> 
> Crossposted to comp.sys.prime, and followup-to set there.

I didn't know that. My final year undergraduate project was modifying the 
CPU on a DDP-516, to add/modify some instructions...

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Re: PDP-8 ASCII question Morten Reistad <first@last.name.invalid> - 2016-04-04 16:15 +0200
  Re: PDP-8 ASCII question Bob Eager <news0006@eager.cx> - 2016-04-04 18:23 +0000
  Re: PDP-8 ASCII question drb@ihatespam.msu.edu (Dennis Boone) - 2016-04-04 20:08 -0500
    Re: PDP-8 ASCII question Morten Reistad <first@last.name.invalid> - 2016-04-05 03:48 +0200
      Re: PDP-8 ASCII question Jim Wilcoxson <prirun@gmail.com> - 2016-04-05 06:27 -0700
        Re: PDP-8 ASCII question Morten Reistad <first@last.name.invalid> - 2016-04-05 16:05 +0200
          Re: PDP-8 ASCII question Greg Field <greg.field.au@gmail.com> - 2018-11-04 18:26 -0800
            Re: PDP-8 ASCII question Jim Wilcoxson <prirun@gmail.com> - 2018-11-05 07:15 -0800

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