[Coco] CoCo3: banking in ROM-Packs

Pere Serrat psergm at gmail.com
Wed Apr 11 10:03:14 EDT 2018

Hello John,
you are right, the cartridge is based on /CTS but we have some cartridges
that are bigger than the std 16K and I have been looking at their contents
and found some differences:

ROM Name            1st 16K chunk                2nd 16K chunk
                           data in last 256 bytes     data in  last 256 
Arkanoid                 $ff all bytes                    $ff all bytes
GFL Football II        data (dif. values)            $ff all bytes
Mind-Roll                data (dif. values)            $ff all bytes
Predator                  $ff all bytes                    $ff all bytes - 
Same for next 2 parts
RAD Warrior           $ff all bytes                    $ff all bytes
Rampage                $ff all bytes                    data (dif. values)
Robocop                  $ff all bytes                    $ff all bytes - 
Same for next 6 parts
Silpheed                  $ff all bytes                    $ff all bytes
Super Pitfall            $ff all bytes                    data (dif. values)

No problem with the ones that have data till the end of the second chunk
as it is mapped to $8000-$bfff and so should be easily accessible
But those two that have data till the end of the first chunk will be mapped
to $c000-ffff and the last 256 bytes would not be of use for them ...

Unless, as Darren Atkinson has explained to me, the program contains
code to 'map' the last 8K of these ROMs to slot #3 ($6000-$7fff) and that
way it could read all these data bytes using $ffa3 or $ffab

In fact all this burden has been caused because I am playing with the
CoCo-Flash module and have found a few problems with three of those
big ROMs: Mind-Roll, Predator and Robocop
I might have the wrong files so I was trying to find a way to read them
as I have those cartridges. I could copy them in parts to save to disk
to be flashed later
Any ideas would be grealy appreciated


Previous message
Message: 7
Date: Tue, 10 Apr 2018 16:13:53 -0400
From: "John W. Linville" <linville at tuxdriver.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Subject: Re: [Coco] CoCo3: banking in ROM-Packs
Message-ID: <20180410201353.GB3128 at tuxdriver.com>
Content-Type: text/plain; charset=us-ascii

The ROM addressing is still based on CTS*. The address decoding
in the CoCo knows nothing of the bank switching, so CTS* will still
be generated the same way.  Therefore each bank will have the same
hole at the end.

John W. Linville Someday the world will need a hero, and you
linville at tuxdriver.com might be all we have.  Be ready.

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