[rescue] PDP 11 Madness

Carl R. Friend crfriend at rcn.com
Thu May 6 18:46:51 CDT 2010

    On Thu, 6 May 2010, Jochen Kunz wrote:

> According to http://www.village.org/pdp11/faq the 11/20 maxes out at
> 24 kB core. So you will be limited to UNIX V[1-7].

    It may have been wishful thinking on DEC's part, but the 11/20
I'm starting at right now has an 18-bit address register (or at
least that's the number of switches on the front panel for an
obviously 16-bit machine), so memory-management options either
were available or absolutely planned for the 11/20.

    The worst problems one is likely to run into with a /20 is
I/O space -- especially I/O space that has DMA capability.  The
one I have has three SPC slots in it, none of which have NPR
capability.  You'll be able to shove an RX-01 controller into
the basic chassis, but forget about anything more advanced than
that unless you have an expansion chassis.

| Carl Richard Friend (UNIX Sysadmin)            | West Boylston       |
| Minicomputer Collector / Enthusiast            | Massachusetts, USA  |
| mailto:crfriend at rcn.com                        +---------------------+
| http://users.rcn.com/crfriend/museum           | ICBM: 42:22N 71:47W |

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