I should have specified perf / watt. Pentium M's came and cleaned up compared to P4s, there was a fair bit of time there when, excluding massive power hungry desktop monsters, a beefy laptop with a Pentium M could easily beat an average desktop with a P4.

And IIRC pipeline stalls on the P4 hurt, badly.

Oh and RAMBUS, I had forgotten about RAMBUS. That also hindered the platform.