Intel's 90nm Pentium M 755: Dothan Investigatedby Anand Lal Shimpi on July 21, 2004 12:05 AM EST
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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.