P4-M
- This is just the mobile version of the P4A. That's old technology btw. It's running on 100Mhz core (400Mhz FSB) and comes with 512K of L2 cache and 2nd Generation SpeedStep technology
- It would seem that the P4-M is a (relatively) high performance mobile chip but this is not the case (and I'll get to the Centrino later). Why? Because of the pipeline problem I mentioned at the beginning. The P4M/P4A needs a high clock speed to compete with both the AMD chips and the Centrino and on a mobile platform, high clock speeds are not the norm and thus you'll find the P4-M getting owned left, right and centre. Also, the desktop chips have the advantages like HT (hyperthreading)... which also isnt feasible on a mobile platform.
Pentium-M/Centrino
- Since the P4-M ate dust at not-insanely-high-clock-speeds and was given a licking by the mobile AthlonXP chips, Intel decided to make a new chip, christened the Pentium-M (which caused too much confusion so it was renamed the Centrino -- but they are same thing)
- Right off the bat you'll note that the Centrino is very AMD-ish in that, although it is clocked slower than P4-Ms it outperforms them! Also, as they are designed for mobility, you can downclock them by quite a bit and reduce heat and incrase battery life.
- Although we know the P4 uses a 20 stage pipeline, Intel has not spec'd out the number of piplines on a Centrino although its defintiely between the 10 stages on the P3 and the 20 of the P4. Simply based on clock speeds I'd guess its 12 but that's just a guess nothing more. Again the arguments of pipeline apply (efficiency vs brute force clock speed)
- The Centrino ships with a massive 1MB of L2 cache (possibly to attempt to counter the marketing effect of shipping a slower clocked chip compared to their P4-M processors).
- Remember that schpeil I gave about latencies? According to Intel, the latency of the L2 cache their P4-M is 7 clock cycles ... staggeringly high while the Centrino drops it to 5cycles.
- The AthlonXP-M is adapted from their desktop chips and even though it is "used to" running off slower clocks compared to Intel, it really does start to meet its match when it comes to the Centrino (not by much) but it does (in most cases). AMD still is the king of the hill of floating point operations (as opposed to the older, easier, integer operations)
- Compared to the P4-M and AthlonXP-M, the Centrino is definitely the way to go hands down and will (relatively) dominate both when it comes down to power and performance-per-clock. Techies will argue to you the Centrino comes with built-in wireless support are talking smack. The Centrino is a CPU -- the chipset for that CPU comes with wireless support (albeit 802.11b). The downside to a Centrino is it's pricetag and very poor performance-cost ratio
- There are also different revisions of the Centrino! When you goto a store nowadays and get a Centrino, that will be running a Centrino2003 chip there is word of a Centrino2004 which blows it's 2003 counterpart out of the water in every category from power, performance and battery life (appraoching 6 hours, up from 4 from the Centrino2003). Given the 2004 moniker it would seem to come out this year but I wouldnt expect it until October/November in time for the christmas sell off)
Direct Comparison
P4M
L1 = 8K + 12 words @ 2cycles
L2 = 512K @7 cycles
Speedstep = 2nd gen
P-M
L1 = 32K + 32K @ 3cycles
L2 = 1B @5 cycles
Speedstep = 3nd gen
how much memory will the table have? if it has less than you p4 it will run slower but it has the same there might be a little slower but not that noticable.
Not just that but also consider the speed of the memory
P-M Processors and their approximate P4 Equivalents
Comparison isnt quite that simple when you consider all the variants:
- RDRAM vs nonRDRAM
- Core
- FSB
I have to know if a Pentium M 1.0GHz Tablet will be fast or faster than my Pentium 1.4,
Faster no. Speed is measured in Hz and 1.4Ghz is a bigger number than 1.0Ghz.
Effectively faster... yes. Why? The P4M is a 20stage pipeline as opposed to the much more efficient 14 stage pipeline inthe P-M. Thus clock for clockt he P-M will obliterate the P4M
