Monday, 25 November 2013

Same Same But Faster

After lunchtimes and nights stumbling my way around GNU assembler and linker, Neo Geo hardware and 68K ASM, I've finally managed to replicate my Donkey Kong rendering demo in 100% assembler.

This time 'round, I've got it rendering in both horizontal and vertical orientations, the plan being to develop both variations if practical - even if it means assembling both variations in their entirety and having them side-by-side in the same PROM image (after all, it's only 16KB of Z80 code!).

100% ASM rendering - horizontal and vertical orientations
It's not perfect yet - there are obviously a few nuances of Neo Geo sprite hardware I need to tame - but it's enough to get me started on porting the code. The demo comprises a single render function for the entire screen (which handles either orientation, selected with the controller A & B buttons) and is being called from the demo VBLANK handler (after executing the BIOS handler).

I'm still yet to decide the best approach for rendering in-game graphics, so for now I'll take the 'easy' way out, and maintain a copy of Donkey Kong's 1KB VRAM in Neo Geo RAM, and render from that every VBLANK (as the demo is doing now) until the best solution becomes clearer. I figure if I use macros to address the VRAM it'll be easier to adapt them to direct Neo Geo (and other platform) hardware accesses at a later date, as well as facilitating rotation of the display.

Before I get much further though, I need to step back and configure the linker properly, and I should also set-up the CD version as well rather than wait until the end. Regardless, there's a decent amount of code to port until I get anything at all to show for it, so probably not much to blog about in the next few weeks... although I am attempting to get the NGPACE hardware moving along...

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