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From: grr@cbmvax.UUCP
Newsgroups: comp.os.minix
Subject: Re: Stack growth
Message-ID: <1412@cbmvax.cbmvax.cbm.UUCP>
Date: Sat, 14-Feb-87 01:44:54 EST
Article-I.D.: cbmvax.1412
Posted: Sat Feb 14 01:44:54 1987
Date-Received: Sun, 15-Feb-87 04:57:24 EST
References: <966@ulowell.cs.ulowell.edu> <1565@cit-vax.Caltech.Edu> <1377@cbmvax.cbmvax.cbm.UUCP> <800@vaxb.calgary.UUCP>
Reply-To: grr@cbmvax.UUCP (George Robbins)
Organization: Commodore Technology, West Chester, PA
Lines: 21
Keywords: stacks

In article <800@vaxb.calgary.UUCP> radford@calgary.UUCP (Radford Neal) writes:
>
>For example, on a stand-alone PDP 11, the stack grows down from the top of
>memory, *wherever that may be*. The program is loaded into low memory, which
>is always the same place. So you don't have to re-link all your programs
>when you buy more memory.

Oh mama, grant me patience!  Please look in a PDP-11 reference manual.  All
the original stack limit architeure assumed that the (system) stack sat just
above the interrupt vectors, which do start at zero.  If you put the stack
above the program and data, it will have lunched the system long before you
would get a stack limit warning!

This is not to say that some operating systems didn't do it as you describe.
Also, note that the PDP-11 instruction set makes relocatable loading trivial,
since instructions support PC relative addressing, and address constants
need only have the load point added to them...
-- 
George Robbins - now working for,	uucp: {ihnp4|seismo|rutgers}!cbmvax!grr
but no way officially representing	arpa: cbmvax!grr@seismo.css.GOV
Commodore, Engineering Department	fone: 215-431-9255 (only by moonlite)