Intel Core

It takes something special to make Intel introduce a new name for its processor. In the last ten years, we’ve seen only the Celeron and the Xeon, so the all-new Intel Core promises something special. Here, we’ll explain the technology behind the chip, what this means in terms of performance and the impact the new chips could have on notebook and PC design.

The Core is actually two new processors: the Core Solo and Core Duo. Based on the core formerly codenamed Yonah, they’re making their debut in notebooks and form the heart of the new Centrino platform. As the names suggest, the Core Duo processor has two execution cores, continuing Intel’s drive toward multicore processing and multithreaded applications, while the Solo contains just one core and will find its way into lower-cost machines.

Intel’s current roadmap includes Pentiums for several months to come, but the chances are that either this or the next generation of Yonah will become the primary desktop processor too, finally ousting the Pentium for all mainstream applications.

The technology

The Core Duo processor isn’t simply two Dothan Pentium M cores combined on one die. The Core is a significant evolution, although its architecture is heavily based on the previous 90nm generation. Along with the new Presler-cored Pentium Extreme Edition (see p75), the Core processors are the first models to be fabricated using Intel’s newest 65nm process.

The clichéd comparisons to the width of a human hair are now more or less redundant: 65nm (0.0065 of a millionth of a metre) is in the same order of size as a virus and significantly smaller than bacteria. This has helped Intel to fit two cores onto a die only slightly larger than that of the latest Dothan-cored Pentium M (90mm2 as opposed to 84mm2 for the older part). Although this isn’t quite the miraculous feat it might sound – most of the area of the die is taken up by the same 2MB of Level 2 cache – it’s still an impressive piece of engineering, and the total transistor count has increased by 11 million for a total of 151 million overall.

What is truly impressive, however, is the fact that, despite having double the cores, the total power consumption of the Duo has remained largely consistent with the Pentium M. This is partially thanks to the 65nm process, but substantial savings have come from a raft of incremental measures.

Power-saving features

Put simply, the Core’s smaller transistors mean lower drive current per transistor and thus lower power consumption. It isn’t all plain-sailing, though: as transistor sizes have decreased, problems with leakage current have increased. The practical upshot of leakage current is that even when a transistor is nominally switched off it still wastes energy, but Intel has invested heavily in developing ultra-low-leakage fabrication techniques for the 65nm parts that require them.

Core also introduces Dynamic Cache Sizing. This is a power-saving measure that allows the processor to flush out the contents of the cache to main memory. The areas of cache that have been cleared can then be switched off until needed again. In addition, flushing the whole cache to memory allows each core to go into a lower-voltage Deep Sleep mode. Previously, there needed to be a voltage safety margin to ensure the integrity of cache data, but once it’s been flushed to system memory that requirement is removed. The result is a new Enhanced Deeper Sleep power state (known as a C state) for even lower idle power consumption.

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