I'm pretty sure that a single core of a modern CPU is much faster than Pentium 4 at the same clock rate. As a result, I believe that a proper parallelized code running on a modern quad core CPU would be much faster than the same code running on 4 P4s.
This is what I meant. While I looked over some benchmarks I saw that a single Haswell thread for example seems to be 3-4 times faster than a Pentium 4.
