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Path: utzoo!mnetor!seismo!mimsy!aplcen!osiris!phil
From: phil@osiris.UUCP (Philip Kos)
Newsgroups: comp.arch
Subject: Re: An idea I'm kicking around
Message-ID: <1070@osiris.UUCP>
Date: Tue, 21-Apr-87 12:30:58 EST
Article-I.D.: osiris.1070
Posted: Tue Apr 21 12:30:58 1987
Date-Received: Wed, 22-Apr-87 05:28:44 EST
References: <12884@watnot.UUCP> <1061@aw.sei.cmu.edu>
Distribution: comp
Organization: Johns Hopkins Hospital
Lines: 28
Summary: not necessarily

In article <1061@aw.sei.cmu.edu>, firth@sei.cmu.edu (Robert Firth) writes:
> In article <12884@watnot.UUCP> watmath!watnot!ccplumb (Colin Plumb) writes:
> 
> >What if JSR moved the return address into another register?
>
> .... The PDP-11 puts it on
> the SP stack, ....

Yeah, well, not if you tell it not to.  As I recall, the PDP-11 JSR
instruction allows you to specify *any* of the eight "GPRs" to hold the
current PC contents, after pushing the old value of the specified register
onto the stack.  (Among other purposes, this was used [with R5] for
passing the address of an in-line FORTRAN parameter address block - the
scheme was referred to in RT-11 manuals as "subroutine linkage".)

And to think I was feeling left out back when everyone was discussing the
old IBM machines in comp.misc, just because I never wrote assembly language
on anything more primitive than a 370!  I guess I'm not as young as I
thought I was... :-)

-- 
                              ...!decvax!decuac -
Phil Kos                                          \
The Johns Hopkins Hospital    ...!seismo!mimsy  - -> !aplcen!osiris!phil
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