Intel Core 2 Duo, the technical lowdown

 

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By David Fearon, Deputy Editor, PC Pro

Posted on 14 Jul 2006 at 10:24

Smart memory access

It's a common criticism of the Intel platform architecture that the memory subsystem is both bottlenecked and a victim of high latency. The shared front side bus represents the bottleneck; the need to communicate with main memory via the north bridge chip increases latency.

AMD cuts out all this with its on-chip integrated memory controller and dedicated memory interface. But Intel has largely overcome the problem with its 'Smart memory access' design. Rather than relying on low latency to grab data from main memory on a just-in-time basis, the system loads data into the Level 2 cache before it's needed.

The upshot is that latency isn't an issue, since if the data required by the CPU is already loaded into the Level 2 cache, main-memory latency is hidden. The system effectively increases the bandwidth of the main memory interface itself by making maximum use of available throughput, continually pre-loading.

That's not to say increased memory bandwidth isn't needed; the new ICH8 memory controller hub, which supports 800MHz DDR2 RAM, made a notable difference in our tests: swapping 800MHz memory for 667MHz DIMMs brought the application benchmark score for the E6700 down from 1.65 to 1.55; a 6 per cent drop.

Advanced digital media boost

This is the latest catch-all term for all the specialist SIMD (single instruction, multiple data) instructions and registers, now incorporating MMX, SSE, SE2 and SSE3.

There are no new instructions, but performance has been increased by a tweak to allow one complete 128-bit execution step in a single clock cycle rather than two, effectively doubling the speed of 128-bit operations.

Intelligent power capability

Decreasing the frequency is one reason why the Core 2's power consumption is much lower than previous Intel desktop chips, but there are other enhancements at the logic level.

Core 2 has finer granularity in its ability to shut down the parts of the processor that aren't being used at any particular moment, making for a much reduced power consumption figure in average use. There's always a slight performance hit when powering areas of the processor back up, though, hence not all the power-saving features of the mobile version of Core 2 are included in the desktop chips.

The TDP (thermal design power) of the E6700 is 65W; that's half the rating of a Pentium D 960. Intel hasn't yet released the TDP figures for the other desktop parts, but based on published figures for the Woodcrest Xeons, the E6400 should come in around the 40W mark, and the Extreme Edition X6800 at about 80W, which is still 50W lower than the 3.73GHz 965 Extreme Edition part.

Conclusion

The basic models are very fast. The high-end ones are faster still. All are low power. And, tellingly for AMD, the fastest score we've seen from an FX-62 system is 1.45 - some 12 per cent slower than the E6700 here. The only disappointment with Core 2 is that there's nothing bad we can say. Intel is back on the desktop with a vengeance.

You can read the full version of this article in the September PC Pro (issue 143), on general sale 20 July. As well as a technology guide, there are also four exclusive reviews of machines based on the new chip.