Also, CPUs at the time were simple enough that you could just add up instruction timings and know how fast the code would run. But now you can get dramatic performance improvements by making assumptions about how today's microcoded superscalar pipelines happen to invisibly schedule instructions out-of-order, and compilers automate the required bookkeeping.
The Pentium Pro was not the average CPU for playing Roller Coast Tycoon though. Although in the process of writing this comment I found out that the P5 series was the first Superscalar processor and that Roller Coaster Tycoon needed at least a P90, so it may well have taken advantage of it.
