In general, a processor's power can be determined by 3 things:
1. Clock Speed
2. Bus Speed
3. Cache (L1, 2, and 3)
Clock speed is a large indicator of a processor's power. It is the speed at which a processor can execute instructions. While we might think of an instruction as "Save a file", really that might consist of hundreds of instructions. As software becomes more complex, it becomes necessary to have the ability to execute more instructions per second.
A processor with a 1.0 GHz clock speed can execute 1 billion instructions per second. The unit here used is Hertz, which is also Cycles Per Second. So Giga-Hertz is a Billion-Cycles-Per-Second measure. Pentium 4 Processors generally have higher clock speeds, so they have an edge over Pentium M processors in this department. However, other factors are in play . . .
Bus Speed is the speed at which the processor communicates with the computer. Bus speeds are measured in Mega-Hertz, millions of cycles per second. So, Pentium M processors in general have 400-MHz buses. This is not bad, but Pentium 4m Processors have between 533MHz and 800Mhz bus speeds. Point to Pentium 4 again.
To understand cache, you have to understand the layered storage architecture in the computer. The computer uses several types of storage which increase in speed based on how often the data is accessed. The slowest is the hard drive of course. This is secondary storage. Above that, you have the system memory. This is faster, but not as fast as Cache.
Cache is a small portion of memory that is super-fast. It comes in levels. Level 1 is the fastest, and there's usually about 64 Kilobytes of this. This cache is integrated onto the chip. This is the fastest storage the processor has available.
Level 2 Cache used to be stored on the motherboard. It was called Pipeline Burst cache, and back then, if you had 256K of it, you were smokin'. But starting with the late Pentium IIIs and Athlon XP's, L2 Cache was integrated onto the chip.
Some chips integrated Level 3 cache as well. But the only chip I can remember having L3 Cache was the Xeon and Pentium Pro . . .
In any event, it's fast ram storage for the processor. Pentium M's have 1MB Cache in the "Banias" core chips (1.6 GHz and below), and 2MB Cache in the "Dothan" Chips (1.6 and above, designated by number 725 and above). Pentium 4's have 1MB.
So the one edge (performance-wise) that the Pentium M processors have is that they have more Cache (in some cases).
So why the Pentium M?
It uses much less heat and power than the Pentium 4. So in a laptop, it is much cooler and lasts longer than a P4 laptop.
Intel Centrino Technology is simply the Pentium M processor and chipset plus integrated Wireless B or G.
A caution: Celeron M processors are Decontented Pentium M processors. Ken has mentioned this many times (in fact if you google "Decontented Processor" you will come up with about 6 posts of his. :))
What that means is that it's a Pentium M processor with less speed and features (like Cache and Bus Speed) than the Pentium M.
It's like when they sell you a Toyota in South Florida but want to charge extra for Air Conditioning.
Hope that helps.
i was wondering.
how fast is
1.0GHz Pentium M processor, a 1MB L2 cache??
i mean can anyone compare that to pentium 4 x.x gigahertz?
and what is L2 cache? do i need alot of it?
i am trying to buy vaio TR series. and i LOVE it except the fact that it has LOW speed ghz...