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MEGA PET (a "look and feel" C65 ROM patch)

  • The PET 8296 (named CBM 8296 in Germany) was besides the PET 4032 the first computer I used in school for programming. I still like the PET typical green color monitor and the "professional" 80 char display (at the 8296).


    Here is the start screen of the PET 8296 emulated with VICE:



    I combined this "remaining love" with my playing around with the C65 and build a "PET ROM" for the MEGA65.


    With this patch I tried to let you feel like you are sitting in front of a PET 8296 while you are using your MEGA65 (Nexsy/Xemu).


    I tested the patched ROM with the Nexsy board and the Xemu emulator (xc65 and xmega65).


    The patch "pet_a" include all modification done with patch "AH".

    Additionalty I changed the char rom areas $9000 to $9FFF and $D000 to $DFFF with the appropriate char values from the German PET 8296 ROM (so you have also the umlauts in it). I can not simple copy the memory areas, because some chars are on another place in the C65 ROM.


    Because a PET "have to" use a green color monitor, I changed the default palette colors to a green color palette.


    At least I had modified the start up routine in the C65 ROM to let the start screen look like it's a PET:




    Just to get sure:


    Be aware that this patch is NOT a PET emulator!


    Only the "look and feel" of a PET is simulated.


    You are still using a MEGA65 with all advantages and disadvantages. :D


    All available C65 programs (3 in number :whistling: ) can still be used and also the color palette can be changed in a program to see colors again.



    To patch the original 911001.bin C65 ROM with the attached patch, use the patch instructions as described in this post.


    bspatch 911001.bin patch_pet_a.bin 911001_pet_a.bin


    Rename the "911001_pet_a.bin" to "MEGA65.ROM" to use it with the MEGA65 or Nexys board.


    In the attached zip file there is also a D81 disc image with two little demo programs (one for showing all characters and the other for showing all 16 colors in bars).





    Here is a look using MEGA PET with the C65 Notepad:


    A monitor session with disassemble lines:



    The MEGA PET after "GO64": :D (The C64 mode uses the PET characters)




    Maybe you want to try another "look and feel" for your MEGA65? If so, have fun with it! :)

  • Haha, that's cool :D I thought about trying to "port" things like C128 BASIC (or maybe Plus4) to MEGA65. Surely the same, the nature of the hardware won't change, but in this case even the basic dialect does (though for sure, POKEs wouldn't do the same, and it may take some efforts all the gfx/etc commands work. That can be useful to run programs written for C128 (Or plus4) BASIC at least. Though I don't think it is terrible useful :) And it's a much bigger work, as not the C65 ROM should be modified but the original C128/Plus4 to work on the MEGA65 hardware. Though I am not sure if BASIC 10 is backward compatible with those, so it's totally pointless to do ;)

  • I thought about trying to "port" things like C128 BASIC (or maybe Plus4) to MEGA65. Surely the same, the nature of the hardware won't change, but in this case even the basic dialect does (though for sure, POKEs wouldn't do the same, and it may take some efforts all the gfx/etc commands work. That can be useful to run programs written for C128 (Or plus4) BASIC at least.

    I'm not 100% sure, but isn't the BASIC 10 downward compatible to the BASIC 7 of the C128 and to BASIC 3.5 of the Plus4? So I think, a pure BASIC 3.5 or 7 program (without any POKE/PEEK stuff) will run on the BASIC 10. :gruebel

  • The question is, are those treated as bugs, which were intended to be fixed some day if C65 is ever released back in the day, or not. C128 is interesting, since I have the suspect even C128 ROM has unimplemented commands originally wanted to be on the Commodore LCD (like the OFF, if I remember correctly which is turns out does something on C-LCD).

  • Basic 10 is not even backwards compatible to itself: ...

    We should only talk about the latest available C65 ROM: 911001. That should be the reference for the BASIC 10.


    It makes no sense to use and look at any older ROM, because they are only former steps of the development of the ROM. Why should anyone use an older and even more unfinished ROM as the latest one is?

  • I'm not 100% sure, but isn't the BASIC 10 downward compatible to the BASIC 7 of the C128 and to BASIC 3.5 of the Plus4?

    Stuff like DO/LOOP/BEGIN/BEND is compatible, but all the instructions for graphics were re-designed for the C65.