[Coco] MESS CoCo Emulation

[Arthur Flexser]

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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