Date: Tue, 7 Sep 1999 22:40:58 -0700 (PDT)
From: "Steven M. Schultz" <sms@moe.2bsd.com>
Message-Id: <199909080540.WAA17669@moe.2bsd.com>
To: pups@minnie.cs.adfa.edu.au
Subject: Re: Diff between 11/20 and 11/45?
Sender: owner-pups@minnie.cs.adfa.edu.au
Precedence: bulk

Howdy -

> From: Carl Lowenstein <cdl@mpl.ucsd.edu>
> Abbreviated due to fading memory over the years, but refreshed by some
> of the current discussion.  The patch was zero-length but involved more

	It has been a long long ('quad'? ;)) time since I first encountered
	the problem.

> than the one instruction.  Something similar to:
> 
> 	MOV SP, -(SP)		MOV SP, R0
> 	MOV (SP), R0		MOV R0, -(SP)

	Ah, thank you for bringing that memory back to the front of the brain!
	If R0 is available for that then yes indeed that'll do the trick very
	nicely.

> on the stack.  Without doing both a SRC and DST operation on SP in the
> same instruction, which is the thing that is incompatible across different
> processor hardware.

	The 11/45 (and 70) behave as "expected" as do the KDJ-11 systems
	(11/73, etc) so unless a person had an 11/40 (or a /20) around it
	would be fairly easy to get bit by the "feature".

	When it comes time for MMU "features" I know of one difference between
	the KDJ-11 and the other members that had an MMU (11/44, /70, etc). Was
	fun tracking it down but not something I'd want to do again ;)

	Steven