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From: moroney@world.std.spaamtrap.com (Michael Moroney)
Newsgroups: alt.sys.pdp11,comp.sys.dec,comp.os.vms
Subject: Re: QBUS Prototyping
Date: Tue, 19 Apr 2011 15:34:46 +0000 (UTC)
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Johnny Billquist <bqt@softjar.se> writes:

>One rumour has it that it was developed in order to extend some patent 
>or something.

I heard the same little birdie, and it certainly makes sense, to make the
instruction set unique.  Someone could probably find another processor or
processors that essentially implement each of the other PDP-11
instructions.  Kind of like deliberate errors added to copyrighted maps.

>Another would be that they were just crazy.

That certainly would have helped!

>I've not seen a single compiler use the subroutine linkage that 
>explicitly makes the MARK instruction meaningful, and besides. It is not 
>usable if you have split I/D space.

I won't claim there is one, esp. if it doesn't work with split I/D space.

>> (next question, which compiler(s) used it?)

>I have no idea.