SpiceWare's Blog

Excellent work from Nathan as always - the game is really coming along great!

 

The only thing I don't like is the movement of the ship. It feels a little bit sluggish in acceleration, and the deceleration seems a little too jerky (when friction is enabled). Would it be possible to tweak this a bit to closer match the arcade version?

 

Chris

Awesome! the ship rotation is very smooth. I should have done 32 rotation positions in Rip-Off

I've figured out some tricks for rotating sprites using Photoshop. I may have to go back and revisit Star Castle now.

Yeah, I'm not happy with the ship's ac/deceleration yet either. I need to put some time in MAME to get a better feel for it.

 

I also need to tweak the shots, they don't leave the ship if you're traveling at your fastest speed (and shooting in the direction of travel).

Very good

So, does Stella emulate that ARM processor now? Or does this game only use DPC processor? I have not found any information on this on Stella's web page. It only says "Added MAMCR handling to the Thumb ARM emulation code. Note that MAMCR isn't actually emulated, it is just ignored for now."

So, does Stella emulate that ARM processor now?

Yes, ARM CPU emulation was added in version 3.4. While it runs the code, it does not emulate the cycles it takes to run the code. As such, you need to test on real hardware to make sure the ARM code doesn't take too long to run. If it takes a little bit too long the Atari's screen will jitter. If it takes a lot too long the Atari will crash. The reason for this is that the 6507 is provided NOP commands while the ARM code is running. If the 6507's program counter goes past the end of the 4K cartridge it'll try to run non-existant code outside of the 4K ROM space.

 

It only says "Added MAMCR handling to the Thumb ARM emulation code. Note that MAMCR isn't actually emulated, it is just ignored for now."

The ARM chip in the Harmony/Melody has a bug with it's cache implementation. The cache is called MAM(Memory Acceleration Module) for some reason and the only way to prevent the bug from crashing the program is to partially disable the cache. That's done via MAMCR (the MAM Control Register). The original ARM emulation in Stella would "crash the program" if the program changed MAMCR, so I used to have to make "Stella builds" and "Harmony builds". I don't have to make extra builds now that Stella ignores MAMCR.

The only thing I don't like is the movement of the ship. It feels a little bit sluggish in acceleration, and the deceleration seems a little too jerky (when friction is enabled).

I revised the physics in the latest build.