BackBit Pro Cartrdige for the TI-99/4A

[RXB]

Even if a new file format is needed for Backbit, I just need to know how to make them as I have been updating RXB (Rich eXtended Basic) for 30 years now.

Currently RXB 2022 uses 3 8K banks of ROM the 2 lower banks 1 and 2 are like normal XB but a write to >6004 turns on ROM bank 3.

Thus a write to >6000 is ROM bank 1 and >6002 is ROM bank 2.

 

By the way RXB uses 5 of the 8K banks of GROM too.

[+acadiel]

Yep, extra ROMs over two have never been formally standardized - I think everyone implements them slightly differently.  

• Most common is .c and .d, (old maximum of 16K), but if you keep going for carts over 32K ROM, you'll run into .g which is GROM.  
• Some do a .c, .d, .e, and .f for 32K ROMs.  
• Some just put the entire ROM (no matter how large) as a binary and the multicart/emulator/simulator knows it needs to split it into 8K chunks.    

I'm preferential to the last one, as:

1. No modification needs to be done to the ROM.  Only a tag for reverse 8K banks (379) vs normal 8K (378/377) needs to be done, or CRU.
   1. The tag can be either a field in a JSON/XML blob, or part of the filename
2. People don't have to worry about multiple files being split and which order they go in

 

As far as the non-standard what I like to call "split banking", it's much easier to take the handful of carts that do this (i.e. TIXB and TI Calc) and just make whole 8K ROMs that contain the entire address space as it exists in both states.  Makes the logic a bunch easier, and this is traditionally how these cartridge ROM images have been made and exist in the community today.  

 

Mini Memory and MBX are different because of the RAM.  Those will require special handling regardless.

[evietron]

I will support any standardized community format as long as it can be contained in a single binary file, and doesn't have an extensive amount of parsing required. If you want to have a custom file extension to describe what format a raw binary is in, I am okay with that.

 

As I have a multitude of projects for different systems in development at once, the best place to ask questions and post feature requests is on the BackBit Forum (forum.backbit.io).

Edited October 28, 2022 by evietron