Intel Takes the Fast Train to Clarkdale

The new 2010 models have been in your neighborhood auto dealer's showroom since last fall, but what Intel calls its "New 2010" Core processors went public only this month. The dual-core "Clarkdale" Core i3 and Core i5 desktop CPUs not only make the old Core 2 Duos effectively obsolete, but make some significant changes to the formula introduced with the Core i7 "Nehalem."

The new processors utilize a dual-die format. One is a 32-nanometer-process (down from 45nm) processor core, while a separate 45nm die incorporates a new graphics core alongside the memory and PCI Express controllers. The integrated graphics component is the major change in this processor line, which requires the dual-channel DDR3 memory and PCI Express 2.0 16-lane controllers to shift off the CPU core and onto the secondary die with the GPU.

Building graphics into the processor is a major change for Intel, especially after its much-hyped and oft-delayed "Larrabee" graphics chip failed to materialize and was subsequently canceled. That led industry wags to reopen the old "Intel sucks at graphics" conversation, which does have a lot of history behind it. However, Larrabee's misfires were aimed at the top of the graphics totem pole. The truth is that Intel has had some notable successes in entry-level desktop graphics, albeit at the chipset level.

The Great Integrated Graphics Trade-Off

In keeping with that tradition, the new, on-die Intel HD Graphics core is not going to have enthusiasts tossing out their Radeon HD 5970 cards -- it's essentially a slight upgrade from the popular GMA X4500HD-level graphics found on many Intel chipsets. Sure, there are two more execution units and the clock speed is slightly higher at the top end, but we're not looking at a drastic shift in GPU features or design. Intel continues to link its integrated HD Graphics to the DirectX 10/Shader Model 4.0 specification, with support for Windows 7 and Blu-ray acceleration.

Graphics clock speed is set at 733MHz for most of the Core i5 parts, with a 900MHz exception for the Core i5-661. Why that single CPU gets a graphics speed boost is a real mystery, especially as the higher-end Core i5-670 is relegated to 733MHz as well. These latest Core i5 models also get back on Intel's Hyper-Threading Technology bandwagon, which boosts multithreading performance a bit and was inexplicably left off the feature set of the earlier "Lynnfield" Core i5.

Where on-die graphics can really pay off is in memory bandwidth. On a typical integrated-chipset GPU, the core is linked to a standard system bus, and is not only limited to the speed of your installed DDR2/DDR3, but also has to compete with other components for memory access and latency. By incorporating the GPU on the CPU die, Intel has eliminated one of the historical barriers to integrated graphics performance, and the new GPU is now linked directly to the high-speed memory bus.

Due to this, graphics performance on the Core i5-661 is noticeably faster when compared to an Intel chipset with GMA X4500HD graphics. But this is a backhanded compliment, and if your most demanding graphics program jumps from 5 frames per second on the X4500HD to 8 fps using the integrated GPU, you quickly realize that "faster" is a relative term.

Unfortunately, what Intel gains in GPU memory bandwidth, it loses in system memory performance. Now that the integrated DDR3 controller has been moved from the CPU core to a separate die, it adds latency to the transfers; hence, memory performance lags behind a comparable Lynnfield processor. Along with slightly higher power usage (due to the onboard GPU), this is the main caveat of buying the 2010 Core i3/i5 processors. Even if you intend to buy a separate video card, you are stuck with the slower memory controller.