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Comment by vidarh | Hacker News Reader

Not that surprising, given the CPU in the NES is a second sourced near-6502 (Ricoh 2A03) though running a bit faster apparently. But there's nothing in there that's hard to do on a C64 (and in fact before this there was The Great Giana Sisters, released in '87, that was so similar - including a near identical first level - that Nintendo threatened to sue and it was taken out of the stores; but of course "everyone" had copies soon enough anyway)

EDIT: Here's a video of the C64 version of Giana Sisters: https://www.youtube.com/watch?v=8teXm6723-g&t=1309s

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I think the NES's PPU is a lot more powerful in some ways than the C64 VIC-II chip. The NES's PPU supports multiple background layers, priority, pixel collision detection and has up to 64 sprites on screen at once - albeit with some limitations on how many are on each scanline. The VIC-II can only do 8 sprites at a time without scanline raster tricks (and if we count those the NES can do more than 64 too)

IIRC the NES PPU only supports one background layer. You can just change the scroll position mid-frame to give it the illusion of multiple background layers.

See here for some clever examples of this technique. Everything that's overlapping is done with sprites:

https://youtu.be/ZGyFQ9aRp_U?t=579

You're right, I was thinking of the SNES which had multiple background layers.

It's not near-6502 it's an exact 6502. Die-shots show the exact same transistor layout; even the decimal section is there but disabled.

There are differences in terms of some IO pins. But yes, the changes are minimal.

Oh wow, nostalgia! Giana Sisters was absolutely fantastic. I played it to death. My NES owning friends were kinda grumpy about how good it was.

I'd like to give a shoutout to machinae supremacy https://www.youtube.com/watch?v=XKkmyMKbPKE

Chris Hülsbeck https://www.youtube.com/watch?v=XKkmyMKbPKE

and all the guys at https://www.slayradio.org

for keeping the scene alive!

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