[rescue] Re: UNIX PC/3b1?

Dave McGuire rescue at sunhelp.org
Thu Jun 7 20:48:16 CDT 2001

On June 7, dave at cca.org wrote:
> mcguire at neurotica.com writes:
> >  The other issue is split I/D space.  Some later Unix implementations
> >require it, while not all pdp11 processors have it.
> >  I can give you details of which ones do what if you're interested...
> Yeah - I'm curious about the following:
> PDP-11/45
> PDP-11/70
> PDP-11/23
> (The first two because they're historically important, the last because
> I've got one.)

  The pdp11/45 has split I/D space (indeed, it was the FIRST pdp11 to
have split I/D space) and an 18-bit address bus.  A fast machine.
Circa 1972.

  The pdp11/70 has split I/D space and a 22-bit address bus.  A VERY
fast machine.  Circa 1975.

  The pdp11/23, if memory serves, does not have split I/D space.
All but the very earliest rev of the KDF11-A pdp11/23 processor boards
have a 22-bit address bus.

       -Dave McGuire

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