The Pentium was not just pipelined but also superscalar; it had two pipelines (U and V). U implemented all instructions, V only implemented a subset of simpler ones, and only when using simple (prefix-less) encodings.

As the CPU was not out of order, to execute two instructions per clock you had to pair them so that the second one was simple, and did not use the output of the first one. Existing code and most compilers around at the time were generally bad at this, but things like inner render loops in games could make a lot of use if you wrote them in assembly.