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From: cuda@ihuxf.UUCP (Mike Nelson)
Newsgroups: net.micro.cbm
Subject: Re: Commodore 64 Stack
Message-ID: <2869@ihuxf.UUCP>
Date: Thu, 24-Apr-86 08:28:35 EDT
Article-I.D.: ihuxf.2869
Posted: Thu Apr 24 08:28:35 1986
Date-Received: Sun, 27-Apr-86 05:42:04 EDT
References: <493@unccvax.unccvax.UUCP> <641@nicmad.UUCP>
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 36

> In article <493@unccvax.unccvax.UUCP> jeh@unccvax.UUCP (Jeffrey Holman) writes:
> >
> >    Can anyone tell me if there is a way to reset the stack pointer in ML?
> >I want to move the location of the stack to some bigger area of memory for
> >use in a possible compiler.  I am afraid that this is impossible since I
> >have been unable to find any reference to the stack pointer location in 
> >memory.
> 
> If I remember the processor correctly, the stack pointer is actually coded
> into the chip program, making it non-movable.
> -- 
> 
>               ihnp4------\
>             harvard-\     \
> Mr. Video      seismo!uwvax!nicmad!brown
>               topaz-/     /
>              decvax------/

It really is movable or else it wouldn't work very well as a stack pointer.
:)  I haven't messed much with my computer lately but it should be fairly
easy to manipulate even though probably not directly writeable. The stack
exists in the 1st page of memory where a page is 256 bytes.  0 page is
used extensively by the operating system.  Several tests would have to
be performed.  First, I don't know if the pops are volatile, destroying the
memory as it is read.  I doubt it.  Next try to find where the stack is 
by pushing values on the stack and testing for those values through the
range of the stack.  Then perform the appropriate number of pops or pushes
to arrive at the address you wish.  If you wish to push over data without
erasing it you would probably have to read the particular location and
push that data back in the same spot.

If all else fails, drag out your handy laser and etch you a data path
and read command into the 6510.

Good luck.
Mike Nelson