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
Problem #1: Can't Use Desktop Chipsets
Although the Pentium M uses the same bus as the Pentium 4, there are two limitations that prevent you from using the Pentium M on regular desktop motherboards or chipsets. The first limitation is that the Pentium M's pin-out is quite different from that of the Pentium 4, despite the similarity in number of pins and socket layout to the Socket-478 Pentium 4s. So, even if the Pentium M could fit in a desktop Pentium 4 board, it still wouldn't work - it's like plugging a USB cable into a FireWire port; even if you could make it fit, you're not going to be transferring anything over that cable.What about a simple converter that modifies the pin-out of the Pentium M to be compatible with a Pentium 4? The reason why a Pentium M to Pentium 4 converter can't be reliably made is explained by the second limitation: the I/O buffers on the Pentium M operate at relatively low voltages (1.05V) while the I/O buffers on a Pentium 4 operate at the CPU's core voltage (1.3V+). In order to work properly with a Pentium M, the North Bridge (MCH) must be able to operate at similarly low voltages, which none of the current desktop chipsets are able to do. There is also additional drive circuitry that is present on the chipset to help deal with operating at such low voltages, which aren't present on desktop Pentium 4 chips.
The problems resulting from these two limitations are three-fold:
- Desktop Pentium M motherboards must use mobile chipsets, which are $10 more expensive on average than their desktop equivalents, leading to more expensive motherboards.
- Current desktop Pentium M motherboards are about 6 - 12 months behind the design schedule of mobile Pentium M motherboards, meaning that they are all using Intel's 855GME chipset, unfortunately, and not the latest mobile 915 chipset. The biggest implication here is that this means that all current generation desktop Pentium M motherboards feature only a single channel DDR333 memory controller.
- The upgrade path for desktop Pentium M motherboards will be quite limited. The problem is that you're pretty much guaranteed only to be able to upgrade to faster 90nm Dothan based Pentium M processors, which aren't going to get many speed bumps between now and when they are replaced by Yonah (which won't work in current motherboards). Remember that the Pentium M is designed with a clock speed limit in mind and that limit is very low, so don't expect too many speed bumps between now and the end of the year (our roadmaps indicate only one new speed this year, that's all).
Facebook
Twitter
RSS
77 Comments
View All Comments
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)