The only way that a software can be optimized for Pentium IV is to use CPU's SSE2 instructions, but they doesn't exist in other Pentiums processors and also aren't compatible with AMD's 3dNow instructions. Also the code must be done in assembler and today almost nobody use Assembler for making software (I do). Software will run faster with Pentium IV or Athlon than with others processors, that is due the more elaborated hardware of the Cpu and not due the not universal optimizations.

Stupidity also evolves!