Taking Core to the Edge: Intel unveils 6-core Xeon CPU

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Santa Clara (CA) – There is no doubt that the Core micro-architecture will have a special place in Intel’s history. Core reclaimed the performance crown from AMD, it put Intel on the power-efficiency track and it brought the first quad-core processors in a portfolio that has delivered more than 200 different processor models over the course of two years. While the first-generation Core architecture will see its first successors in Core i7 (Nehalem) CPUs later this year and may slowly begin phase out in the second half of next year, Intel today showed once more the potential of Core with the first 6-core processor – which is not only evidence of the scalability, but also indicates the limits of this architecture.

Leaving aside the fact that Core was the main product that brought down AMD to its knees and its obvious dramatic consequences, the basic aspects of this micro-architecture have been fascinating. From a simple strategic view, Core transformed Intel’s processor business from a desktop-centric development into what is essentially a mobile processor environment. Pretty much every processor (with the exception of the Xeon 7100, Itanium and some Celeron processors) has an energy-efficiency focus and was originally thought out as a mobile CPU. Power consumption levels have been cut dramatically – to 65 watt at Core 2 Duo’s introduction, down from 100 - 130 watts of the Pentium D series.

Two years ago, we all wondered: How far can Core scale? Today we know that at least in clock speed, there was not much progress – at least as far previous generations are concerned. We heard that Core 2 Duos were running relatively stable at 4-4.5 GHz in Intel’s labs, but the company never saw a reason to go above 3.5 GHz – up from 2.66 GHz at introduction. However, we saw progress in terms of the number of cores. In late 2006, Intel launched the Kentsfield multi-die quad-core processor and now the Dunnington multi-die six-core chip. They may not be as sophisticated as AMD’s single-die quad-core CPUs, but they certainly leverage lots of manufacturing flexibility and enable the company to have achieved the 6-core mark first. AMD plans to release the single-die 6-core “Istanbul” processor in H2 2009.

Dunnington arrives in seven flavors, four and six cores, three different clock speed levels, six rack-optimized models and four different thermal design power (TDP) specs. Considering the fact that all processors are running at more than 2 GHz, the TDPs are impressive. But there are signs that the limits of Core may be in reached in the not too distant future.

Besides the fact that you will need Intel’s data and pricing sheet to figure out which of the processors has how many cores and what power consumption and the notion that these are Intel’s most expensive processors right behind the Itanium mainframe CPUs and a 32-socket system can cost you $87,000 just in Xeon processors (but will give you 128 processing cores and a whopping 512 MB in L3 cache in exchange, we got stuck a bit on the “max” power rating, which is substantially above the TDP, which Intel recommends to system builders as a design guideline for servers.

According to Intel the max power rating is a more theoretical value that means that those processors can consume that much power - 170 watts in terms of the X7460 – but only under special scenarios, such as synthetic benchmarks. While Intel concedes that the TDP does not indicate the maximum power a processor can draw, the TDP is based on observations under “various high power applications”. However, a “worst case real world application”, which can hit or exceed the TDP is possible, according to Intel, and may trigger the chip’s Thermal Control Circuit (TCC) when the processor is running in a “worst-case thermal condition” (at a case temperature at or near 64 degrees Celsius). In such a scenario, the operating frequency and input voltage will be reduced to cool down the chip. Intel says that, in such a worst case scenario, there will only be brief “brief instances of TCC activation [which] are not expected to impact the performance of the processor.” (More details: Xeon MP 7400 datasheet, 3.1 MB PDF download)

Due to the relatively high power rating, the X7460 is only recommended to be used in 2U systems, while all other 7400-series processors can ruin in 1U rack-optimized servers. Intel claims that a sustained power consumption of more than the indicated TDP is unlikely and systems should be designed around this rating as a result, but the company’s rating is certainly an average TDP and not a max TDP rating, which clearly shows that 2.66 GHz 6-core Core processors are hitting the limits of what products make sense and which not. Intel may be able to scale Dunnington a bit higher, but we don’t expect substantially higher clock rates – and the company does not have to: By the time AMD’s first 6-core arrives, Intel will have Nehalem in place and have more flexibility and room for Dunnington’s successors.

It is unusual for Intel to provide max power consumption ratings for its products. For example, the company’s Netburst-based Xeon MP processors with Tulsa core are listed with the generic TDP rating of 150 watts for CPUs above 3.0 GHz and 95 watts below. IT buyers interested in Intel’s latest processors should have a close look at the company’s new Dunnington processors, which are platform compatible with the 7300-series (Tigerton core). Compared to the 7300-series some quad-core Dunnington processors consume less and others more power (according to the TDP rating) at the same clock speeds, while costing the same money. The 6-core CPUs may be the most interesting reason to look at the lineup, but the privilege of running the first 6-cores will cost $2301 or $2729 per CPU. From a power perspective, certainly the most impressive product in this family is the L7455, which runs six cores and 12 MB of L3 cache at 2.13 at a TDP of 65 watts – and a max power of 85 watts.

The progress is obvious if you take yourself back in time for two years and imagine running six cores within 65 watts. Fascinating.

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