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Path: utzoo!watmath!clyde!rutgers!ames!amdahl!drivax!alexande
From: alexande@drivax.UUCP
Newsgroups: comp.os.minix
Subject: Stack Growth Direction
Message-ID: <913@drivax.UUCP>
Date: Mon, 9-Feb-87 19:12:09 EST
Article-I.D.: drivax.913
Posted: Mon Feb  9 19:12:09 1987
Date-Received: Thu, 12-Feb-87 18:44:49 EST
References: <383@dayton.UUCP> <13647@ti-csl.CSNET> <384@dayton.UUCP>
Reply-To: alexande@drivax.UUCP (Mark Alexander)
Organization: Kludges 'R' Us, Inc.
Lines: 30
Keywords: Stacks
Summary: RTFM

In article <384@dayton.UUCP> joe@dayton.UUCP (Joseph P. Larson) writes:
>Pre-decrement of SP for a push makes the stack grow up...

Wrong.

I quote from the Intel iAPX 286 Programmer's Reference Manual, 1984,
pages B-80 and B-84:

	POP ... The word on the top of iAPX 286 stack, addressed by
	SS:SP, replaces the previous contents of the memory, register,
	or segment register operand.  The stack pointer SP is incremented
	by 2 to point to the new top of stack.

	PUSH ... The stack pointer SP is decremented by 2, and the
	operand is placed on the new top of stack, which is pointed
	to by SS:SP.

Then, from the Motorola M68000 Programmer's Reference Manual, 4th ed.,
page 23:

	Stack growth from high to low memory is implemented with
	  -(An) to push data on the stack,
	  (An)+ to pull data from the stack.

That's straight from the equine oral orifice.  As the bumper sticker
says (in another context), "Read The Book."
-- 
Mark Alexander	...{hplabs,ucbvax!decvax}!decwrl!pyramid!amdahl!drivax!alexande
"This then is my story.  I have reread it.  It has bits of marrow
sticking to it, and blood, an