RTG Duke3d has been around for about a decade. Configured properly it should give you 20ish fps on your '060+rtg setup. Is a little faster than novacoders version too
tried it last night on my CSII 68060 with CV64 with Duke Atomic and it kept complaining about not finding the duke3d.grp file , even though it was there and in the same drawer. It was a Mac version of Duke though.
It ran quite well in Shapeshifter though.
What FLEW was the Marathon series-made my wonder why Alien Breed 2 3D is so slow.
