Intel's 90nm Pentium M 755: Dothan Investigated
by Anand Lal Shimpi on July 21, 2004 12:05 AM EST- Posted in
- CPUs
Sixteen months ago, Intel released a confusing little thing called Centrino; it wasn't a new processor or chipset, but rather a "technology". Intel pumped billions into the marketing of this technology and even to this day, we still see the same "What is Centrino?" question. But unlike most multi-billion dollar marketing campaigns, Centrino wasn't a hip name masking uninteresting technology; instead, Centrino encompassed one of the most impressive microprocessor architectures to ever come out of Intel: Banias.
We had all heard about Banias, which was officially named the Pentium M, for almost two years, but most shrugged it off as a rebranded Pentium III. With the Pentium 4's power requirements climbing, it was all too easy to believe that Intel would just go back to a much cooler running architecture for the future of their mobile processors. Pentium M became known as a Pentium III with the Pentium 4's Front Side Bus long before it ever shipped, before the first benchmarks were ever run. But as we just finished mentioning, this processor was far from rehashed technology.
Last year, we took an in-depth look at the Pentium M and came away from the experience extremely pleased. Our sentiments were echoed by manufacturers and end users alike, with the Pentium M and Centrino notebooks that use the processor selling extremely well and truly enabling high performance, long battery life, thin and light notebooks. Offerings like IBM's Thinkpad X series grew extremely popular among business users while more stylistic options, like the Sony VAIO X series, brought a new meaning to portable, with Pentium M designs weighing less than 1.8lbs. What Pentium M brought Intel was the portability and form factor advantages of Transmeta, with the performance that Intel customers were used to.
To put it bluntly, Intel's Pentium M was an instant success and well deserving of the success at that. But in our long running history at AnandTech, we've never been quite satisfied with one successful product - we want to see improvements, perfection of the perfect, if you will. And thus, it was no surprise that we were quite eager to take a look at the follow-up to Intel's 0.13-micron Pentium M, code-named Dothan.
We first heard about Dothan before Banias ever hit the streets as Pentium M. If you'll remember from our original article on the Pentium M, Banias only missed its target completion date by a matter of days. One by-product of on-time execution was that a number of architectural tweaks that the design team wanted to get into Banias had to be left out, a sacrifice made to preserve on-time execution. As soon as the Banias design was complete, those final architectural tweaks and enhancements that didn't make it into the first Pentium M incarnation were at the top of the list for its successor. As a result, Dothan is best viewed as a more polished evolution of Banias, with higher clocks and more cache made possible by Intel's 90nm process.
But unlike Banias, Dothan wasn't the perfect student on time to its launch; instead, Dothan was released after months of delays. Intel has already publicly released the reason for Dothan's delay. There was apparently an analog design issue with Dothan; more specifically, a PLL was too jittery. Dothan was actually in the hands of OEMs back in January, but the yields were extremely low, thanks to the jittery PLL issue. The solution to the problem required another spin of the silicon, which takes a long time (even longer at 90nm) and resulted in Dothan's lengthy delay.
Being an evolutionary, rather than revolutionary part, Dothan isn't nearly as exciting to talk about as Banias was, but as you'll soon see, that doesn't take away from its worthiness of carrying the Pentium M name.
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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?