Denial

Nice Game! Is there a non cartridge version from this game? I good like to create a tape from the game, but i can not find it. It would need at least 8 KiB expansion. If you have RAM at $a000-$bfff you might have luck with the version on zimmers (SYS 41001). https://www.zimmers.net/anonftp/pub/cbm/...

For completeness, this is the one I used: skramble_rabbit_software.tap

I'm glad my version worked out for you!

I did a single file version of this a while back (15 years ago apparently ), here: skramble.prg.
Never got around to uploading it anywhere and haven't tested it that much to be honest, but feel free to test it out.

Usage of the stack pointer as a general register [...] The stack pointer is not a general purpose register. It is a special purpose register intended for indexing into the 65xx hardware stack. Ok then, "general" register. It can index data on the stack, and it can serve as temporary stora...

The commands I haven't used so far were TSX and TXS. At Aitsch's suggestion, I looked into the topic of stacks in more detail. Then the following occurred to me. Normally the X regsiter is pushed onto the stack via TXA and PHA. This takes a lot of time, 5 cycles. A better solution would be to store...

For an example of a working VIC-20 transfer routine you could examine JiffyDOS for the VIC-20. There are quite a few drive -> VIC-20 implementations (e.g turbo load) but not very many VIC-20 -> drive. JiffyDOS has both. All in all doing a transfer routine is quite an interesting, and sometimes frust...

MicroSD makes sense IMO. Allows you to make a more compact design as well. Can you still source the CPLD?

What a bummer, I thought it would be so easy. Optimizing vector calculations is not trivial. Asymmetric multiprocessing on an 8-bit system is not trivial either, especially since you have a bandwidth limited link. Make sure you are optimizing the right thing! I’d start with the multiplication, then...

I wrote a small program that can measure the speed. I hope it is calculated correctly. Interrupts are periodically disabled during IEC access. Jiffies won’t be accurate. You’ll have to manually use a timer. I don’t think you will get any gain doing single multiplications, but matrix rotation could ...

Why do you need to copy? The (vector) graphics is supposed to be pre-rendered into a shadow bitmap and then blitted over to the display bitmap to reduce flicker. There is not enough RAM accessible for the VIC to hold two bitmaps of the given size, hence the need for a memory copy instead of "j...

Hi, thanks for the tips. Do you have a fast IEC transfer routine to share? Not a ready made one for the vic20, no. Bacause of the clear and copy time, i use a 144x224 pixel screen. There i like to clear the screen size 144x160. This needs a little bit more than 14.400 cycles, in addition, there is ...

I had forgotten the great website Codebase64. There is enough source code there to try out. I hope to be able to do multiplication and division for 3D calculations this way. This should happen in parallel while the screen is being deleted and the data is being loaded from the buffer into the screen...

Maybe the VIC is mirrored at $910x? I don’t remember. In the real world, the VIC is definitely not mirrored at $910x—otherwise, it would be mirrored all the way from $9100 to $91FF, as it is pretty lazy about decoding the addresses itself. It is possible that Victor's decoding is enabling it on too...

Doesn’t explain it, but may give a clue: The VIA decoding is very trivially done so CA4 and CA5 are more or less directly selecting VIA1 and VIA2. This means that both can be selected in parallel. As these chip selects are active high this happens at $913x. At $910x none would be selected. EDIT: may...