Articles: CPU

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Dual-core Intel Xeon 2.8GHz

And here’s the true hero of this review. The processors we have described above are hardly a surprise for anyone as they have long been on the market and have been thoroughly explored by the users while the dual-core Xeon has appeared just recently and is scarcely available as yet. Intel introduced its dual-core Pentium D back in the first half of 2005 but then didn’t hurry to release a dual-core Xeon. Why? Because unlike the rest of the Xeons, the dual-core model from this series has no counterpart among Intel’s desktop CPUs. To make a worthy reply to the highly successful dual-core Opteron Intel has to do some additional engineering work. The result is going to be presented to you right now.

So the core of the new Xeon is codenamed Paxville and is a concatenation of two Nocona cores. Thus, the main difference of the Paxville from the Smithfield core that is employed in the dual-core Pentium D is not only in its targeting at servers and workstations but also in the bigger amount of L2 cache memory. The Smithfield has two cores with 1MB L2 cache in each whereas the Paxville has a 2MB L2 cache in each of its cores or 4MB in total. Only Xeon MP CPUs, intended for multi-processor systems, could boast such a large cache before, but now the cheaper CPU for dual-processor configurations comes with 4MB of cache, too.

Strangely enough, Intel didn’t wait for its 65nm tech process to come into operation to produce the Paxville. The company won only a couple of months with the earlier announcement, but then had to make processors with a really gigantic core. It is not a wonder then that Paxville-core CPUs are unavailable on the market.

Xeon (Nocona) on the left; Xeon (Paxville) on the right

But it was not only the manufacturing cost of the dual-core Xeon that suffered from such a big die size. Intel had to reduce the frequency of the new processor not only below the frequency of singe-core Xeons on the Nocona core but also below that of the dual-core Pentium D to ensure stability and acceptable heat dissipation. The clock rate of the only announced model in the dual-core Xeon series is 2.8GHz, but even this couldn’t keep the heat dissipation and power consumption of the Paxville within normal limits. The TDP of the dual-core 2.8GHz Xeon is 135W, which is 23% higher than that of senior single-core Xeon models. Mainboards for the Paxville processor must have a reinforced voltage regulator as a result and more advanced power supplies and coolers may also be necessary. For example, our dual-processor system with two Paxville-core Xeons would not work on a 460W power supply and we had to replace it with a 600W analog. As for cooling, the all-copper coolers included with senior single-core Xeons coped with the dual-core processors as well.

Although the high heat dissipation prohibits using the Paxville processor on the existing mainboards, it uses the same Socket 604 as the older Xeons. There is no need to introduce a new socket because the CPUs are fully pin-compatible. Moreover, the dual-core Xeon uses the same 800MHz Quad Pumped Bus and is compatible with Intel’s E7520 and E7525 chipsets. The downside is that the system bus bandwidth is now shared among four cores and the speed of communication between the CPUs and memory and between the different CPUs may suffer (Intel recognized this problem and is now preparing new chipsets with two independent FSBs).

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