I just ported BBCMicro core to my de0ns version of MiSTer. One thing I noticed was strong screen flicker caused by the default interlaced mode. I remember that interlaced mode is how the original computer works, so in this respect the core reproduces it perfectly. However my eyes suffer watching the interlaced screen on my TV. Not only that, one of my VGA LCD monitor could not even display such video mode when using scan doubler option and the other VGA flat panel displayed strong simulated flicker as well. I was able to disable it and thought you might find it useful. The mod is very simple, just disable the interlace in the code: mc6845.vhd, line 357, like this
Code: Select all
--if r08_interlace(0) = '1' then
-- odd_field <= not odd_field;
odd_field <= '1';
basically this mod enables only the odd fields. That's it. Recompile the core and you are done.
Please note I haven't tested this mod extensively, just played a few games, but it seems to work fine so far. It's quite possible some video effects may be lost in certain games, therefore keep your original core if you want to preserve full software compatibility.
Edit: Just thinking about it a bit more, maybe I should have added another option into the menu to disable and enable the interlace...