Linux and the Desktop Pentium M: Uncommon Performance

Summing it all up

Overall, Dothan provided us with some sporadic, but interesting, performance gains and losses. Unfortunately, Pentium M just doesn't scale similarly to Pentium 4 or Athlon 64 in any application, although it does seem to mimic the performance of one or the other occasionally. On our OpenSSL tests, Dothan continually out-nudged even our mid-range Athlons, but then fell far behind in compilation and some content creation tests.

There are, however, bottlenecks in the performance. High speed memory is something that our Dothan severely lacked on Linux, and we would certainly appreciate the next generation Alviso chipset to support something a little faster than DDR400. However, as Pentium M is a notebook chipset first and a blade/desktop chip second, the demands of low power notebook memory certainly take priority over a niche SFF/HTPC crowd.

The first surprise in our analysis came with the SQL database tests. Our windows benchmarks have shown in the past that the additional L3 cache can be quite helpful for database applications, and the 2MB L2 cache found on the Dothan plays a huge part in boosting performance. On the other hand, the additional cache might have been the same reason why GCC performed so poorly - although we hope that the Linux compile test was just a fluke (Update: Please see the note on the Compiling page. We believe we had an isolated fluke with the PATA driver that limited our performance). Other benchmarks put Dothan right in the upper middle of the pack, usually beating out the Pentium 4 offerings, but occasionally beating out the best that our Athlon 64s could produce as well.

Dothan isn't the miracle chip that we would have liked it to be. For starters, it is horribly expensive still. The 2.1GHz Dothan that we previewed today runs at around $500, and the motherboard costs another $270. For just a barebones configuration, our Pentium M desktop runs at around $1000. Granted, the overclockability on Pentium M seems outstanding, but finding slower, cheaper Dothans in socket 479 pin configurations may be a problem.

Unfortunately, we are only getting a small glimpse of the story here today. Our preliminary benchmarks on Windows show that Dothan does some awesome things on Windows; the compilers and operating system get a little more help from Intel in the design phase. Unfortunately, the extremely powerful and free Linux compiler remains dully unaware of many of the benefits that Pentium M has to offer, and as a result, it gets hurt painfully under the default or wrong compile flags.

All in all, Dothan does some very exciting things. The promise of cool, efficient powerhouses - from Intel, nonetheless - certainly has our attention. We will be keeping a very close eye on Pentium M over the next few months, particularly with the upcoming Alviso launch. If Dothan's Linux performance keeps up this well on the 855 chipset, we can't wait to see what it does on faster memory and the 915 Northbridge.