Intel's 90nm Pentium M 755: Dothan Investigated
by Anand Lal Shimpi on July 21, 2004 12:05 AM EST- Posted in
- CPUs
Final Words
Banias was revolutionary; it changed the shape of the mobile CPU world and it changed how we perceive mobile chip design to be pursued. It would be nice if the same mobile-oriented design methodology spread to companies like ATI and NVIDIA. Maybe then we would truly be able to game while on the go.Dothan, as an update to Banias, leverages Intel's 90nm process and some architecture tweaks to not stun us, but to keep us happy with the Pentium M platform. At 2.0GHz, the Pentium M 755 is easily the best chip that money can buy for a notebook. Clock for clock, it's faster and uses less power than Banias - there's really no reason not to like it.
If you're using your notebook for office applications and even for content creation applications, there's no beating the new Pentium M. Even developers will find short compile times, competitive with that of a similarly clocked Athlon 64, possible with the Pentium M at lower power usage as well.
What the Pentium M isn't, however, is as strong of a media encoding or workstation processor as either the Athlon 64 or Pentium 4. Partially constrained by its 400MHz FSB and single channel memory interface, the Pentium M is not the successor to the Pentium 4 that many will make it out to be. In many ways, the Pentium M is much like Intel's version of the Athlon 64, sans memory controller. The short pipelined design and accurate branch predictor give the Pentium M a nice and high IPC, similar to the Athlon 64, which give it strength in areas like business applications and are also responsible for its high performance in our compile tests.
With Intel's vision for the future being centered on media encoding and content creation, the Pentium M is the last thing that Intel would want to build their future desktop CPUs around. That being said, the Pentium M is quite possibly the best solution that Intel has for the office PC. It would be nice if Intel used the Pentium M as the basis for its desktop Celeron processor, instead of just a castrated Pentium 4.
The Pentium M will continue to be an excellent mobile chip, and the next incarnation of the Pentium M should be yet another revolution as it may even receive multiple cores as a part of Intel's overall threading strategy.
On the desktop, we may see features like micro ops fusion and some of the Pentium M's power saving technologies make their way into the Pentium 4's eventual successor. Dropping Prescott and moving towards Dothan would be a step back, using each architecture for their strengths and borrowing technologies for use in another would make much more sense for the future of Intel's microprocessors.
In the more short term, we may see some motherboard manufacturers make Pentium M based motherboards for desktop usage. Shuttle, in particular, is currently working on a small form factor box based on the Pentium M. That should be out by the end of this year.
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nserra - Wednesday, July 21, 2004 - link
#3 I agree. Banias is a better chip. It would be nice to see Banias at 0.09 with 1MB cache, would be smaller, cheaper and a lot more chips per waffer, but Intel isn't interested in these yet, at least maybe a Celeron line when Banias phased out.Isn't Ati 9100 chipset compatible with Banias and P4 compatible? A bios change or something more wouldn’t do the trick?
Matthew Daws - Wednesday, July 21, 2004 - link
Interesting read. Some comments though: the Dothan has a HUGE L2 cache, which people, in a thread over at Ace's, suggest gives it a large edge in many applications (there were complaints that it excels in SpecInt simply because of this, and with very large datasets, performance rapidly tails off). Nothing wrong with that, but it might explain why the Dothan has issues with media-encoding and the like, where the volume of data is so large that the size of the L2 cache becomes less important.Also, the test was a little bit of comparing apples to oranges. I see why this was done: to try and give a laptop-like playing field. But Dothan is almost certainly highly optimised to run with, say, single channel, slow RAM. By forcing this on Athlon64 and Pentium 4 desktops, which are optimised for fatter memory channels, you are slightly crippling performance. As such, it's probably a fair test for laptop performance, but probably doesn't indicate how a Dothan-like desktop chip would hold up. This might explain how well it holds its own against the Athlon64 and beats the P4 in many tests.
Anyhow, good to see a great test of Dothan! Cheers, --Matt
xsilver - Wednesday, July 21, 2004 - link
Just a question... I thought the new sucessor to the prescott was going to be the derivative of the dothan -- eg merging back the mobile and desktop solutions? I'm wrong right? So what exactly are they going to replace prescott with?morcegovermelho - Wednesday, July 21, 2004 - link
Where are the Athlon 64 3000+ scores in Sysmark 2004? (page 8)DigitalDivine - Wednesday, July 21, 2004 - link
interesting to see that we are going back to the old days when intel and amd matches each other clock for clock. a 1.8ghz centrino about the same as a 1.8ghz athlon64.still another note that the p4 is still king in media encoding.
overall a nice review.
adntaylor - Wednesday, July 21, 2004 - link
Excellent chip. However, it's bloody expensive. At $637 it is exactly the same price as a 3.6GHz Prescott 560 or right between Athlon 64 3500+ and 3700+, so it's not a good choice for the desktop.Also Anand's comment "...it's faster and uses less power than Banias" is not quite accurate.
Under full CPU load, yes this is certainly true but, as you'd expect from 90nm, the leakage power has shot right up, meaning that in its low power states, the CPU is draining a great deal more power than Banias. How much time does a laptop spend idling relative to flat out? My guess: quite a bit. I'd still choose a Banias in my laptop for that reason alone.
Still good article, and I'd love (from a purely academic point of view) to see what this baby could do when coupled up with a dual-channel memory interface and a good desktop chipset!
sprockkets - Wednesday, July 21, 2004 - link
Probably the best heat vs. performance processor out there, at least for x86. Why Intel is dumb to shove Prescotts which use 5x more power for the same performance is beyond me; I would get this for a desktop quicklike.Of course, we have Intel's TDP instead of what the processor may acutally put out on worst case conditions. That and we don't know what the Athlon 64 at 90nm will put out, at least at 2.0ghz, since all they are doing is a few tweaks to the core (isn't it smaller than 100mm?) That and I guess if you really meant unpatented, that was what to make sure no one really knows why it's so great?
mkruer - Wednesday, July 21, 2004 - link
I’m glad that Intel seem to be moving in the right direction with the Dothan, but I do have a question. Why on half the benchmarks is the Athlon benchmarks missing?