Intel Launches Low-Power Xeon LV Chip for Servers

Published: March 15, 2006

by Alex Woodie

As Intel promised it would do at the big Intel Developer Forum shindig last week, the company this week delivered its first very low power Xeon chip for servers, one that consumes a lot less electricity and generates a lot less heat than a normal Xeon server chip. This chip, code-named "Sossaman," is being sold as the Xeon LV, and like other chips in the Core microarchitecture that Intel unveiled at IDF, it is based on a modified Pentium M processor, originally designed for laptops.

While the future "Woodcrest" Xeon processors due in the third quarter of this year have all kinds of neat gadgetry, such as 64-bit memory support, on-chip instruction set virtualization, and a new pipeline, the Sossaman Xeon LV chip is a variant of the current "Yonah" Core Duo processor for laptop machines that has been equipped to support symmetric multiprocessing and use DDR main memory with error correcting electronics. The SMP support in the Sossaman chip only scales to two sockets, though, but because Sossaman is a dual-core processor, customers can cram four cores into a single machine or blade.

Of course, you can do this with current Xeon processors, but the "Paxville" dual-core Xeon DP chip is running at 2.8 GHz peaks at 135 watts (it's so called thermal design power, or TDP). A dual-core Sossaman chip runs at a relatively icy 31 watts. This is a big savings in electricity and power used, obviously--almost 200 watts in a dual-socket blade server, where heat density is one of the big issues.

But the Sossaman Xeon LV chip, which uses Intel's latest 65 nanometer chip making process, does not support 64-bit applications and, at 1.66 GHz and 2 GHz clock speeds using the less powerful Pentium M core (the Xeon DPs and MPs are based on the Pentium 4 core), the performance you get out of the Sossaman is a lot lower, too. The trick is to get the price/performance and the performance per watt down, and the Sossaman chip most certainly does this, which is why it will be attractive to certain kinds of customers, particularly those who like the blade server form factor. The Sossaman chip has an on-chip 2 MB L2 cache that is shared by both cores. (The future Core server chips will also have shared L2 caches on chip.) The chip plugs into the "Lindenhurst" E7520 chipset, which supports DDR2 main memory running at up to 400 MHz, which burns 30 to 40 percent less energy per MB than DDR main memory running at 333 MHz; up to 16 GB of memory is supported in two-socket machines using the Sossaman chip. Sossaman has a slightly slower front side bus, at 667 MHz, which means it has a little less bandwidth available. But it is also clocking slower, so that should not affect performance. (Initial rumors this year had Sossaman pegged at 3 GHz with an 800 MHz front side bus. That part may have existed on a whiteboard somewhere, or in someone's imagination.)

Intel says that the Sossaman chip has about twice the performance per watt of the "Irwindale" single core Xeon chips, which plug into the same chipset. Compared with a single Irwindale Xeon DP processor running at 3.6 GHz with 2 MB of L2 cache, the dual-core Sossaman offers between 2.17 and 2.93 times the performance per watt. What Intel has not said is what the actual performance is compared to Irwindale or Paxville Xeon DPs. Let's just say if the performance were higher, Intel would say so. And the SPECjbb2005 Java benchmarks and SPECintRate2000 benchmark that Intel cites in its literature are conveniently not posted on the SPEC site as we go to press, so we can't yet tell you the difference in performance.

The Sossaman chip is also very inexpensive, at $423 for the 2 GHz version and $209 for the 1.66 GHz version (in 1,000-unit quantities, as is the norm).

As previously reported, IBM has already pledged its support for the Sossaman Xeon LV processor in its BladeCenter blade servers. In February, IBM announced an improved HS20 blade that is based on Sossaman and said that it could put two of them on a blade and keep the total dissipation for that blade at about 180 watts, including processors, memory, chipset, and other electronics. This is about half of what you can do with a regular Xeon DP blade server. IBM's Sossaman blade will be available in April, with a base price of $1,749.

Because Hewlett-Packard can sell blades based on 64-bit Opteron HE processors, which are also available in dual-core versions and which have a 55-watt TDP, the company has decided to skip the Sossaman chip in its BladeSystem blade servers. Dell and Fujitsu-Siemens have not yet announced their intentions for the Sossaman chip, either. Intel is readying an AdvancedTCA blade server that will also ship in April, aimed at network equipment providers and other service providers. HP will apparently resell this blade into the telco space, however, since it is big on the AdvancedTCA form factor.