O_o (./7) :
doom on a 12mhz cpu ... well, forget it
maybe wolfenstein with agressive optimisations (like on megadrive) but only possible on neogeo cd

There's a version of Doom on the ZX Spectrum - uses a 3.5mhz Z80 as its CPU (Basically a slower version of the Neo Geo's sound processor)

I wonder if Doom may be possible on Neo Geo by using a large number of pre-stored pixel sequences (perhaps using less colours). Or maybe even a combination of this technique and mid-line and hsync raster changes.

However I think the Neo Geo's greatest asset is its huge cart capacity so maybe pre-rotated wall blocks and floor pieces can be stored and then scaled by the hardware? This would surely be the fastest way of doing things.

Anyone know how Duke Nukem 3D was made on the Megadrive? Maybe that can offer some clues. As far as I know the cart is just a standard cart - no extra chips. It seems unlikely everything is calculated in realtime since it runs pretty fast. I could be wrong but I don't remember the standard Amiga running anything texture-mapped that fast and that has a blitter.