Differences between the PDP-11/15 and PDP-11/20

Noel Chiappa jnc at mercury.lcs.mit.edu
Wed Aug 3 09:46:48 CDT 2016

    > From: Paul Koning

    > It would have to be a Unibus bridge type device, i.e., it terminates
    > the Unibus from the CPU, and at the other end originates a Unibus with
    > mapped addresses on it.

Oh, right you are - I hadn't worked that out. (Probably because my head
is still full of KT24 stuff, which doesn't have two totally separated
busses. :-)

    > That assumes the KT11-B does only memory mapping, not the other things
    > that other MMUs do (user vs. kernel mode, I/D space .. ).

I don't think it can; those would require hooks into the CPU, and there are
no signs of such, in the pictures.


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