Intel's Pentium M on the Desktop - A Viable Alternative?
by Anand Lal Shimpi on February 7, 2005 4:00 PM EST- Posted in
- CPUs
Low Latency L2 Cache
We mentioned at the start of this review that the Pentium M featured a very large, yet low latency L2 cache - at 2MB for the current 90nm Dothan based Pentium M. But how much low latency are we talking? To find out, we turned to ScienceMark 2.0 and Cachemem.First, let's have a look at the latency of the Pentium M's 64KB L1 cache:
| Cachemem L1 Latency | ScienceMark L1 Latency | |
| AMD Athlon 64 | 3 cycles | 3 cycles |
| Intel Pentium 4 (Northwood) | 1 cycle | 2 cycles |
| Intel Pentium 4E (Prescott) | 4 cycles | 4 cycles |
| Intel Pentium M | 3 cycles | 3 cycles |
With such a large L1 cache, it is difficult to get much lower than 3 cycles, as we see that the Pentium M has a similar L1 access latency as the Athlon 64. What is also important to note, however, is that the Pentium M does have a lower L1 access latency than the Pentium 4E.
But what we came here to look at was L2 cache latency, which matters much more in real world application performance where not everything fits into L1:
| Cachemem L2 Latency | ScienceMark L2 Latency | |
| AMD Athlon 64 | 17 cycles | 18 cycles |
| Intel Pentium 4 (Northwood) | 16 cycles | 16 cycles |
| Intel Pentium 4E (Prescott) | 23 cycles | 23 cycles |
| Intel Pentium M | 10 cycles | 10 cycles |
Here's where things get very interesting - the Pentium M has the lowest L2 cache access time of any of the modern day desktop microprocessors. With a 10 cycle L2 latency, any application that fits within the Pentium M's 2MB cache will most definitely perform very well on the CPU. It is the 10 cycle L2 that allows the Pentium M to be competitive with much higher clocked CPUs in most mobile applications as they are normally office application tasks that are generally very cache-friendly. Keep this in mind as we look at the actual performance numbers of the Pentium M.
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CSMR - Monday, February 7, 2005 - link
The fact is it's an excellent processor for business use (speed, quietness, reliability) and multimedia use (quietness). Anandtech is full of gamers; but there is no denying that using a computer as a media centre is becoming a big thing, or that low-power, quiet operation is necessary. High motherboard prices are because the desktop PM motherboard market is very small. There was a comment in the review that the PM architecture doesn't scale well. I am sure that is so; but what processors do scale well? It's because they don't that everyone is about to go dual-core.bobsmith1492 - Monday, February 7, 2005 - link
Thanks #12 :PZebo - Monday, February 7, 2005 - link
I myself have been guilty of hyping dothan after seeing GAMEPCs "opimistic" review. This should quell that.:DZebo - Monday, February 7, 2005 - link
Anand best review I've read here, thanks a lot, nice to see you scribing again..:)Seems again, like the tech report review, with a comprehensive test suite such as this one dothan has some collosal performance flaws, and simply can't match up the A64 across board. It looses 30 out of 41 benches at same speed, some huge. 2.0 vs 2.0..
I posted in CPU forum how turion/lancaster will be 25W.. could this be the end of DOTHANS laptop dominace?
Brian23 - Monday, February 7, 2005 - link
I agree with #10.bobsmith1492 - Monday, February 7, 2005 - link
Sorry; first time commenting. I couldn't remember my login name before.Anyway, my laptop OCs better than that. Granted, it's a 1.7 to begin with, but the FSB will do 125 easily, with the same ram increase to boot - 420 MHz, with processor at 2.125. It will do a tad bit more, but that's enough for a laptop I'd say.
bobsmith1492 - Monday, February 7, 2005 - link
testKalessian - Monday, February 7, 2005 - link
#6, Oh yeah? Well, give a P4/A64 an SXGP(Super eXtremely Good Performance) setting and stay out of ITS way!Yawn, right now the P-M doesn't impress me at all. Let a CPU built for mobile systems stay in mobile systems until it gets rebuilt for desktops properly.
Great review, learned a ton :)
GnomeCop - Monday, February 7, 2005 - link
I have a 2.0ghz dothan system, I upgraded from an old 533mhz fsb p4.The speed for my work and games are just fine. I have a leadtek GF6800ultra in my system and its the only thing I have to worry about cooling.
CPU is passively cooled and the system is expremely quiet running on a 359watt psu. By the time I need to upgrade, I will be buying a whole new cpu/mobo/everything anyways.
ksherman - Monday, February 7, 2005 - link
seems like an a really good processor for buisness machines, given the L1 cahe speeds... and not much else (snas uber low power consumption)