Having a play.....

Okay, so I'm not doing my mini-game thing, I've been playing with my Super CPU instead. One question thats always got me thinking is what can you do with a superCPU that you can't do with a stock C64 (3D aside...).

Well, heres one: full screen overscan bitmap scrolling. Not using expanded sprites or anything, but using the full bitmap screen AND sprites in the side border. Now... I thought you might actually manage to do that with delayed DMA etc. but drawing into a full screen height would be virtually impossible surely, particually since you have to scroll through 4 sprites.

Well... okay... you COULD kinda do it... kindof... Imagine this...

FULL screen bitmap, delayed DMA scrolls that - great. Now how about the edges? Well, you need sprites there of course. BUT that means you've to smooth scroll through 4 sprites (2 on each side). Well no. Sprites can move in pixels after all, so just move in bytes and move the sprites in pixels to sumulate a normal scroll.

This still means you have to redraw the sprites though, and thats 4 sprites, (say) 189 pixels each. Quite a bit.... well...no...

IF you used another extra sprite on each side, then you can scroll the sprites and bring on new empty ones each frame too, then your only drawing 2 colums or sprites 189 pixels high over 8 frames (along with the bitmap) - which is perfectly doable.

Could make for a pretty cool C64 demo - standard MCM res, full screen/overscan scroller...neat. Course... since you can't change the colours very well in sprites, you'd have to pick 3 normal colours (sades of blue etc)... but still. You could also use character maps of course, which would make scrolling them much easier and would mean you didn't have to use delayed dma, as long as you double buffered the character map.

So the outcome.....A cool demo on a normal 64, and I still need to find an impossible task for the SuperCPU. It's pretty amazing what a stock machine can do if you poke it a little....


(and before you ask...no I have actually written it all, I've just been playing and know HOW to write it....)