Copyright on Vic20 Roms

[RJBowman]

Do many programs use ROM entry points other than the KERNAL jump vectors? I can't imagine that many games would.

[Mike]

Do many programs use ROM entry points other than the KERNAL jump vectors? I can't imagine that many games would.

Your original question was:

Has anyone ever attempted to clean room engineer Commodore compatible ROMs?

... and the answer is: No.

The reasons for this have been laid out in the preceding posts. If you don't believe those are valid reasons, fine. Prove us false.

[srowe]

Do many programs use ROM entry points other than the KERNAL jump vectors? I can't imagine that many games would.

Many of the ROMs I've disassembled use arbitrary entrypoints into both the BASIC and KERNAL. Anything from simple setting an error value to internals of the serial bus.

[groepaz]

This is even much more true on vic20 than it is on c64, since on vic20 you'll use every trick in the book to save valuable ram space

[Schlowski]

Someone tries to do the same for the C64:

http://c65gs.blogspot.com/2019/05/free- ... -roms.html

[Wilson]

Someone tries to do the same for the C64:

http://c65gs.blogspot.com/2019/05/free- ... -roms.html

Ugh. Half the README is trying to justify the legitimacy of the project and its "cleanliness". There's absolutely no way the author hasn't been exposed to disassemblies of the routines he's rewriting. Like Groepaz said, this makes slightly more sense on the C64, where the top-quality stuff is using the ROM very little if at all. But for C64 4K's and such this is going to have the same issues.

This (and the whole C65 project) seems more like an academic exercise than anything. The author even acknowledges that this particular endeavor is likely redundant:

On a related note, it is quite likely that the lack of defence of the copyrights of the ROMs of these old systems over many many years has created an implied license to use and distribute these ROMs.