MiSTer FPGA Forum

I think I found an incompatibility issue with the C64 core in the Space is Broken - great demo by FAIRLIGHT group https://csdb.dk/release/?id=234768. https://www.youtube.com/watch?v=M2fCRbLwU74
In some scenes, artifacts appear that are not visible on real hardware or in the VICE emulator. I've tried various core settings, JiffyDOS, Dolphin DOS, Action Replay, etc. Nothing helped. I think the issue might be due to an incomplete implementation.
Still, I tip my hat to the developers of the core for the immense amount of work they've put in.

I can see that as well, a subtle bug almost like an echo after the register has been tickled. Still that's pretty far out edge case if that's all that's left I wouldn't call this incomplete implementation. Try reporting it on the github repo for a productive outcome.

it doesn't seem to be in c128 core

Yes, You're right.

I think the 128 core is more mature. They probably should be merged at some point like the 2600/7800.

There are already MRA files to make the 128 into a 64, but it has issues with reset.

There was a HUGE kerfuffle at the idea of merging the cores, so I don't expect that will ever happen.

I indeed fixed a few pixel timing issues in the C128 core, this was a result of implementing the turbo and test modes of the VIC-IIe. There's a difference in pixel timing between the NMOS (65xx, original breadbins and earliest C64C) and HMOS-II (85xx, later C64C and C128) versions of the VIC, and the C64 core's timing is closer to the NMOS than the HMOS-II versions.

The C128 core's pixel timing is still not perfect though, as can be seen with this test from Vice: https://sourceforge.net/p/vice-emu/code ... ii_timing/

The reference pictures from that repo show the differences between the NMOS and HMOS versions.

rcade wrote: ↑Thu Dec 07, 2023 1:45 pm

I think the 128 core is more mature. They probably should be merged at some point like the 2600/7800.

There are already MRA files to make the 128 into a 64, but it has issues with reset.

The C128 core is based on the C64 core though... and really the C64 core origins date back 20 years. FPGA64 was developed for the C-One FPGA

There was some rework on the C64 core in the past few days. The commit messages sound like they might relate to the bug you observed (for example you can now select the VIC-II variant). You could try the latest unstable build and see if anything changed.

https://github.com/MiSTer-unstable-nigh ... ble-builds

mapf wrote: ↑Sun Dec 24, 2023 10:49 am

There was some rework on the C64 core in the past few days. The commit messages sound like they might relate to the bug you observed (for example you can now select the VIC-II variant). You could try the latest unstable build and see if anything changed.

https://github.com/MiSTer-unstable-nigh ... ble-builds

I saw the discussion at https://github.com/MiSTer-devel/C64_MiSTer/issues/160.
The last C64_unstable_20231223_1682a5.rbf core correctly runs The Space is Broken demo in both VIC-II variants.