<<<The CPUs in a "Centrino" are P4 processors and they have the 1MB Cache.>>>
Where did you get that from!?!? that is very wrong - a Pentium-M (the CPU of a Centrino setup), is a complete redesign from the P4 "Northwood", hence it is code-named "Banias".
The Pentium-M runs at speeds up to 1.7GHz, and because it does more Instructions per clock than a P4(-m), it will perform more or less like a P4 2.6/2.7GHz. It has 1MB of L1 cache, as stated above, which is selectively switched on or off depending on it's usage. It has revised and improved power-saving technology.
<<<will perform at full speed on battery where a standard P4M laptop on battery loses around half of it's processing power to save battery>>>
It can run at Full speed on battery (AS CAN THE P4-m), for example the Pentium-M 1.6GHz can speedstep to anyone of these speeds(600MHz;800MHz;1000MHz;1200MHz;1400MHz;1600MHz), but as soon as it is not used, the CPU will switch to ultra-low voltage Deeper Sleep to save battery life even further.
The Pentium 4-m on the other hand, can only speedstep from its full speed to, its reduced speed (1.2GHz), but it can do this selectively and instantly (even on battery).
Bear in mind, that for your Pentium-M notebook to be a "centrino", it must use the P-M processor, the Intel Pentium-M chipset, and the INTEL Wireless card.
RaPTuRe
Who's General Failure and why's he reading my disk?