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From: koehler@eisner.nospam.encompasserve.org (Bob Koehler)
Newsgroups: alt.sys.pdp11,comp.sys.dec,comp.os.vms
Subject: Re: QBUS Prototyping
Message-ID: <A$4TJa9Ngfq2@eisner.encompasserve.org>
Date: 18 Apr 2011 08:00:11 -0500
References: <8265dgFs33U3@mid.individual.net> <hps7i9$htt$1@naig.caltech.edu> <hr2d9r$lv$1@Iltempo.Update.UU.SE> <FgC+HafqKJY6@eisner.encompasserve.org>
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In article <FgC+HafqKJY6@eisner.encompasserve.org>, koehler@eisner.nospam.encompasserve.org (Bob Koehler) writes:
> 
>    I never had a PDP-11 with less than 18 bit address space.
>    Instructions could only access 16 bits of it at a time, but the
>    hardware was there to make use of the rest of it.

   Maybe you didn't, but many of us did.  And on PDP-11 with 18
   bit UNIBUS, we had some systems which were limitted to 16 bit RAM.
   (By design, not by purchase).

   No APRs, no need for them.