Porting Stunt Car Racer to the Commodore Plus/4

This is great, but I think a detail about the Commodore 64 wrong. While the VIC-II is indeed bank switched and can only see a window of 16k, the character ROM is only mapped into 2 of 4 possible banks.

The whole thing is confusing since the CPU and VIC-II both have bank switching that operate independently. By default, the VIC sees the character ROM and the CPU doesn't. You can map the character ROM into CPU memory, and it always shows up at $D000. But the VIC-II has it's own banking configuration, which has 4 settings. The 16k VIC-II address space can see exactly one of the 4 16k blocks of RAM: CPU addresses $0000-$3FFF, $4000-$7FFF, $8000-$BFFF, or $C000-$FFFF. In config 0, the character ROM is hardwired to $1000 in the VIC address space only. Same with config 2. But if you use 1 or 3, the VIC-II sees only RAM.

This is burned into my memory, since a common trick was to set up the system as follows:

    1. Set up screen RAM at $C000 
    2. Load a custom character set (usually tiles for game graphics) to $C800-$D7FF
    3. Configure the VIC to bank 3 ($C000)
    4. Set the offset registers on the VIC for screen RAM and the charset (now in RAM)
    5. Use the RAM under the IO space and Kernal ROMS ($D800-$FFFF) for sprites

That config even worked with BASIC which only used RAM below $A000.

If you switch to bitmap mode and don't use sprites, you have the whole 16k from $C000-$FFFF free for bitmaps and you just need to set the VIC offset register to flip pages.

Loved that game!

We didn’t have an Amiga, so I used to go to my neighbours house to play it!

It was so good and so much fun!

Great sounds as I recall. For the time.

Interesting. And thanks for the dose of nostalgia this morning. Spent many hours playing this as a kid on my Atari ST ....

Increasing the framerate of this game seems to have a strong impact on how players perceive the cars and their handling. The feelings of weight and momentum seem all but gone in the 50 fps versions (there is a hack for the Amiga port too).

Apparently the mind interpolates the missing frames better than the engine.

But my Commodore 16 probably still doesn't have enough memory to run this :)

Back to playing Berks I guess :P

My first racing game. I was about 8 years old and it is still one of the racing games I play from time to time.

One of the best demonstrations of the power of the C64: real physics, good AI opponents and a 3D graphics engine that is still unmatched on the C64.

Geoff Crammond is a great game developer.

This article is well-written and interesting. The port on the Plus/4 looks amazing. Great work!

How does Yape compare to Vice for emulation?