I know that the SGDK (libraries and toolchain for Sega Genesis/Megadrive) lets you do what you're asking for, within plain old C. You just do: SYS_setHInt

I know that the SGDK (libraries and toolchain for Sega Genesis/Megadrive) lets you do what you're asking for, within plain old C. You just do: SYS_setHIntCallback(foo); SYS_setVIntCallback(bar); Where "foo" and "bar" are the functions you want to be called during hblank and vblank. Here's somebody showing how to pull off some scaling effects using them: https://under-prog.ru/en/sgdk-image-resize/ https://under-prog.ru/en/sgdk-image-resize/ A lot of recent commercial Genesis/MD releases have been made with SGDK; performance seems quite nice. After all, theoretically, if your libraries go hard enough and lean on macros and/or inline assembler C doesn't need to carry a big speed penalty vs. assembler. I think this is also made possible by the Genesis/Megadrive hardware throwing interrupts during hblank/vblank but don't quote me on that. Of course, the really insane effects still require cycle counting. My understanding is that the Overdrive 2 demo uses heaps of it. It's strictly 50hz only because it's that tightly coupled to various specific timings (also obviously 50hz gives you room for a few more instructions during blanking intervals vs. 60hz) https://www.youtube.com/watch?v=OeGdJk5zb6c https://www.youtube.com/watch?v=OeGdJk5zb6c