[Coco] MESS CoCo Emulation

[Luis Fernández]

Yes in the program game MEGABUG


> Date: Tue, 15 Jan 2013 13:29:52 -0500
> From: flexser at fiu.edu
> To: coco at maltedmedia.com
> Subject: Re: [Coco] MESS CoCo Emulation
> 
> Actually, the most common method used to protect ROMpack code from
> running in RAM was simply to insert a poke to $FFDE to invoke ROM mode
> (which would of course have no effect on a cartridge but would crash a
> RAM copy).
> 
> But Steve Bjork in at least one game I'm aware of used code that
> attempted to write to critical bytes of his program, sabotaging it if
> the program wasn't write protected by virtue of the fact it was ROM .
> 
> Art
> 
> On Tue, Jan 15, 2013 at 9:30 AM, Robert Gault <robert.gault at att.net> wrote:
> > Arthur Flexser wrote:
> >>
> >> Some cartridge games were protected from running from a RAM copy
> >> transferred to the cartridge ROM area.  Does MESS simulate running the
> >> cartridge from ROM, not from a RAM copy?  Canyon Climber, if I'm
> >> remembering right, was written by Steve Bjork, who in his later
> >> cartridge games put heavy protection to keep them from running from
> >> RAM.  (Or does "verified cartridge image in CCC format" mean the
> >> protection has already been removed?)
> >>
> >> Art
> >>
> >
> > Very good point Art. MESS does simulate ROMs to the extent that you can't
> > change memory in the ROM area. That was the normal method for checking for a
> > copy, POKE ROM memory and if it changes crash the program.
> >
> > I've found two different .ccc copies of Canyon Climber. One works with MESS
> > while the other doesn't. For the one that works, it will not work with coco
> > emulation but does with cocoe emulation.
> > This could be a fluke in MESS or the program may be using ROM code from
> > $8000-$9FFF.
> >
> >
> > Robert
> >
> >
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> 
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