Stalvern wrote:use of something called CDFJ.
DPC is the coprocessor/bankswitch scheme that made Pitfall 2 possible. Harmony/Melody has a driver that supports DPC so you can play Pitfall 2 on it. Supports 8K games with 2K ROM of Display Data(basically the graphic data).
We made a new version of DPC, called DPC+, that unlocked the extra resources of the Harmony/Melody. It supports 24K games with 4K of ROM/RAM of Display Data and the option to offload game logic to the ARM (which gets 512 bytes of RAM for variables and stack usage). Display Data is copied from ROM to RAM when the Atari's turned on, and since it's in RAM it can be changed on-the-fly as needed so way more flexible than DPC's ROM based Display Data. DPC+ is used for Stay Frosty 2, Space Rocks, Scramble, and a number of batari BASIC games.
We tried making BUS for even more advanced games using Bus Stuffing, but it failed on a number of consoles so we abandoned it. More info on BUS starting with my reply at the bottom of the first page of topic Bosconian clone comming to the Atari 2600!!!
We took what we learned from BUS, applied it to DPC+, and came up with CDF which stands for Chris, Darrell, Fred. Chris (cd-w) wrote the driver for the Harmony/Melody, Darrell (SpiceWare, me) designed the driver and implemented it in Stella, Fred(batari) created the hardware. CDF supports 28K games with 4K RAM Display Data (no longer copied from ROM) and is optimized for games using ARM code (such as it now gets 2K of RAM for variables and stack usage). CDF is used for Draconian, Mappy, and Super Cobra Arcade.
John needed 1 extra "Jump Datastream" for one of his projects, Wizard of Wor or Zoo Keeper(I don't recall which), so we made a variation of CDF with 2 Jump Datastreams instead of 1. So CDFJ = Chris, Darrell, Fred, John. I'll be using CDFJ for future projects as well, such as Frantic, Timmy!, and SpiceC
(like batari BASIC, but uses C for the game logic).