PDP11 I/O page memory map

Phil Budne phil at ultimate.com
Fri Mar 2 12:25:14 CST 2018

It might be interesting to make a virtual PDP-11 (simulator) that *IS*
more virtualization friendly, and find out how much user code depends
on the existing behavior...  And then write a PDP-11 hypervisor!

BUT existing PDP-11's aren't even friendly restarting after a page
fault, which is required for lesser virtualization (VM), and would be
necessary to simulate memory mapped devices.

I remember how each new generation of MC68K processors had ever larger
trap stack frames to hold internal processor state...

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