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
Jeff7181 - Monday, February 7, 2005 - link
Give the Dothan a speed bump and some dual channel DDR400 and stay out of it's way...MDme - Monday, February 7, 2005 - link
well, now we FINALLY have a comprehensive review of the P-M, it's strengths and weaknesses. While the P-M is good. the A64 is still better.Netopia - Monday, February 7, 2005 - link
Yeah, I was about to say the same as #3.Why did you go to the trouble to list what the AthlonXP system would have in it and then not actually test or reference it anywhere in the article?
I still have a bunch of AXP machines and regularly help others upgrade using XP-M's, so it would be interesting to see these at least included in reviews for a while.
CrystalBay - Monday, February 7, 2005 - link
Hi, I noticed in the testbed an AXP3200/NF2U400 but there are no charts with this setup.Beenthere - Monday, February 7, 2005 - link
It's a pipe dream for those who wish Intel had their act together. It's already confirmed M don't scale well and is not effective for HD computing. It's performance is really some place between Sempron and A64 but certainly not a suitable competitor to A64 nor FX. Just another Hail Mary for a defunct Intel.coldpower27 - Monday, February 7, 2005 - link
Hmm, an interesting review on the Pentium M to say the least. Though are 2-2-2-10 timings for the Pentium M the best for this architecture???0ldman79 - Wednesday, January 26, 2022 - link
It's interesting coming back and reading this after it's all settled, Core 2 seemed to be an evolution of the Pentium M line.Intel did hang the Netburst architecture up, though they added a lot of Netburst's integer design to Core 2 while designing Nehalem. AMD apparently believed that Intel was going to stick with Netburst and designed the FX line, while Intel went back to their earlier designs and lowered the clock speed, massively increased the IPC and parallelism and out-Phenom'ed the Phenom with Nehalem.
Back then Intel believed that Dennard scaling would continue and they'd have 10GHz chips, turns out wider and slower is better.