Diff between 11/20 and 11/45?

Steven M. Schultz sms at moe.2bsd.com
Wed Sep 8 15:40:58 AEST 1999

Howdy -

> From: Carl Lowenstein <cdl at 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

> 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 ;)


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