Yeah, well, the box... I just stumbled upon this from the programmer:
Build.txt
3/19/94 - Optimized routines in assembly for 486's...
....
5/1/95 - Optimized horizontal line assembly code so it doesn't use the awful SHLD instruction any more. This is a good speed improvement for Pentiums only.
build2.txt
10/4/97 - So I tried to optimize Build for Pentium PRO's. I was actually able to get about a 50% speed increase mostly due to avoiding those awful partial stalls. But there are SEVERAL catches: 1. First of all, you need to enable WRITE-COMBINING for video memory to get all this extra speed. ...
note that the last Duke 3D patch v1.5 was from december 1996.
The cheat DNRATE shows the framerate on the top left. The game does demos, but AFAIK no timedemos.
I am curious as to what of aspect of the pentium architecture would make a difference, besides the bus, but don't have a Pentium Overdrive (POD) to test it against my 486s...