Intel's New Core 2 Duo Processors Run Blazingly Fast in PC World Tests

In addition to our lab-built systems, we tested several vendor-supplied PCs. For example, Dell's $3985 XPS 700, a high-end system based on the 2.67-GHz Duo E6700 processor, came with 2GB of RAM, an nVidia GeForce 7950 GX2 Dual-GPU graphics board with 1GB of SDRAM, and two 320GB SATA hard drives in a Raid 0 array. That system (whose price includes a 24-inch wide-screen monitor) also earned a score of 153 on WorldBench 5, well ahead of the 142 posted by the previous top scorer, a 2.6-GHz AMD Athlon 64 FX-60-based Xi system.

But even those notable scores paled in comparison to the performance of the overclocked system that ABS sent us. The $4199 water-cooled ABS Ultimate X9--which shipped with 2GB of RAM, a pair of Radeon X1900 Crossfire graphics boards, two superfast Western Digital 150GB SATA drives configured in a striped RAID array, and a Core 2 Extreme X6800 chip overclocked from 2.93 GHz to run at 3.5 GHz--turned in a WorldBench 5 score of 181. Obviously, this system is not a likely choice for typical buyers, but its score is by far the highest we've seen from a shipping system. And it may indicate how much headroom Intel's Core microarchitecture possesses.

Architectural Improvements

It's unlikely that ABS could have wrung such impressive overclocking performance out of its Core 2 Extreme system if Intel hadn't put a lot of effort into reducing power consumption in the Core microarchitecture.

Intel's previous generation of Pentium Extreme Edition chips drew up to 135 watts of power. The Core 2 Extreme X6800 draws only 75 watts, according to Intel's thermal design specification; and the more mainstream Core 2 Duo parts bump that number down to 65 watts. As a result, ABS had the headroom to dramatically overclock its system. Moreover, the design should enable system vendors to build high-performance PCs in smaller, quieter cases.

Intel developed its Core microarchitecture from the ground up, focusing on multiple CPU cores, high performance, and low power consumption--there's a lot of technology packed onto its 65nm die (shown below). Using lessons learned in building its successful Pentium M mobile CPUs, Intel first improved its mobile line and released the Core Duo CPUs (for details on these chips see " Notebooks Rev Up With Dual-Core Tech "). Then the company set out to strengthen the performance of its desktop chips, while dramatically reducing their power consumption. For example, when your PC is sitting idle or running just a few simple apps, the Core 2 Duo can clock down or shut off parts of its logic to conserve power.

Much of Core 2 Duo's performance advantage over its Pentium predecessors comes from an additional execution unit on each CPU core. (Core 2 Duo chips have four such units per CPU core versus the Pentium D's three per core.) The additional unit per core, plus some clever coding that lets the chip fuse common groups of instructions into single instructions, allows Core 2 Duo chips to outperform Pentium D chips that run at higher clock speeds

A staggering 4MB of L2 cache keeps the higher-end Core 2 Duo chips supplied with the data they need in order to run at full speed, and Intel has carefully tuned their prefetching algorithms, which preemptively cache the appropriate data before the CPU needs it.

While most dual-core chips, including AMD's Athlon 64 line and Intel's Pentium D CPUs, dedicate a certain amount of cache to each CPU core, the Core 2 Duo provides shared access to its entire 4MB of cache. And the chip can distribute that cache between its cores as needed. If one core is churning away at a particularly complex task, it can use most of the L2 cache, while the other core runs a simple task that demands less cache memory.

AMD's Response

Intel has produced a winner with its Core Duo 2 design; and for the first time in years, the company holds a clear performance advantage over its longtime rival, AMD. But while the short-term performance picture may look bleak for AMD, don't count the company out.

AMD plans to introduce aggressive price cuts this month; and later this year, it will launch 4x4, an enthusiast platform that enables systems to use a pair of high-end dual-core chips. Though applications and games capable of taking full advantage of multiple CPU cores are rare as yet, we expect the performance--and price--of 4x4 systems to be quite high.

Looking further into the future, AMD will open up its HyperTransport bus, allowing other companies to design specialized coprocessors and accelerators and drop them onto the same superfast bus that AMD uses to shuttle data between the CPU, RAM, and other key components in a system. Such coprocessors could be built into a CPU package for multisocket systems or designed as add-in boards for a new slot type dubbed HTX.

This initiative, which AMD is calling Torrenza , will debut on the server side, where multisocket systems are already common and where specialized processors could accelerate Java code or database operations. Desktop and gaming applications are farther away; but if demand is high enough, Torrenza-based physics or graphics coprocessors could appear in the next few years.

Ultimately, however, while 4x4 and Torrenza are interesting technologies, neither is likely to have a large mainstream impact. AMD's true answer to Core 2 Duo will arrive in 2007, when it is scheduled to launch its next-generation CPU architecture, dubbed "K8L." K8L and single-chip quad-core processors will be compatible with 4x4 motherboards, according to AMD.

In the meantime, no matter what their budget, demanding PC users have a high-performance option in the Core 2 Duo line, which should keep their processor-intensive applications humming along.