Intel Clarkdale Core i5 Desktop Processor Debuts

Clarkdale Core i5 661

Just to be clear, Clarkdale is the codename used to describe Intel's new mainstream desktop processor offerings based on the Nehalem microarchitecture, but manufactured on Intel's cutting edge 32nm process node. Arrandale is the mobile equivalent--we've got complete coverage of Arrandale posted here.

Core i5 661 Processor

Like other Nehalem derivatives, Clarkdale features Intel Turbo Boost and HyperThreading technologies, in addition to hardware acceleration for AES (Advanced Encryption Standard) and an on-chip graphics core.

As we've mentioned, the Clarkdale chips like the Core i5 661 we'll be looking at here will be produced using Intel's 32nm, 2nd Generation Hi-K process. The processors will feature two execution cores (dual-core), but with HyperThreading will be able to process up to 4 threads simultaneously. The processors will also feature up to 4MB of Intel Smart Cache, an Integrated Memory Controller (IMC) that support two-channels of DDR3 memory at officially supported speeds of up to 1333MHz, with integrated or discrete graphics support. We should note that when discreet graphics are used, the PCI Express lanes dedicated to the GPU may be arranged in either a 1x16 or 2x8 lane configuration, depending on the chipset being used--more on that later. Through new instructions, the Clarkdale-based processors also offer Advanced Encryption Standard (AES) acceleration, yet d the remain compatible with the LGA1156 Socket and 5-series chipset. Although a slew of new chipsets are being announced today as well.

There are few interesting things to note in regard to the integrated graphics core that will be used with Clarkdale and Arrandale. First, although the processors will be manufactured at 32nm, the graphics cores will be produced at 45nm. That means, of course, that the processors will feature multi-chip packages, and the CPU and GPU won't be merged on a single die. The IGP will be called the Intel HD Graphics core, and is derived from existing Intel graphics products. The new core, however, offers much improved performance and a number of new features, for Intel anyway. Mobile versions of the new IGP will also sport a Turbo mode of their own, that ratchets the clocks and voltage of the graphics core up or down, depending on the workload to conserve power or maximize performance. We have more details on the Intel HD Graphics core on the next page.

Core i5 661 CPU-Z Details

To get a glimpse of the Core i5 661's inner-workings, we fired up the latest version of CPU-Z and snapped a few images of the pertinent details.

The Core i5 661's default clock speed is 3.33GHz, but it clocks down to about 1.2GHz while idling to save power. The default clock speed is a result of its stock 25x multiplier and 133MHz base clock frequency (25 x 133MHz = 3.33GHz). With Turbo Mode enabled, however, the Core i5 661's frequency will peak at 3.6GHz. CPU-Z correctly reports that the Core i5 661 features 2 cores, but that the chip can process up to 4 threads, thank to Hyper-Threading technology.

The Cache configuration on the processors consists of 2 x 32K, 8-way associative L1 data caches, 2 x 32K, 4-way associative L1 instruction caches, 2 x 256K 8-way associative L2 caches, and 4MB of 16-way associative L3 caches--exactly half of what you'd find on a quad-core Nehalem derivative.

Overclocking The Core i5 661
Pedal To The Metal

Core i5 661 Overclocked to ~3.8GHz

We also set out to do a bit of overclocking with the new Core i5 661. We should point out that there are no "Extreme Edition" Core i5 processors, hence they are all multiplier locked for higher values and cannot be manually manipulated upwards to increase clock speeds. The only way to manually increase their frequencies is to increase the base clock speed, which by default runs at 133MHz.

To overclock the Core i5 661, we used the stock Intel cooler and an Asus P7H57D-V EVO motherboard. Tp begin, we first increased the processor's voltage to 1.38v and then increased the base clock frequency until our test system was no longer stable. Turbo mode was disabled to prevent any unwanted frequency spikes, but we left HyperThreading enabled. In the end, we came just shy of 3.8GHz, with a BCLK of 151MHz.

At that speed, the chip idled at around 39'C and peaked at about 68'C under load. We believe we were being held back, however, because any BCLK above 151MHz hung the system hard when Windows was loading. We'll be looking into this further, and will keep you appraised of the situation.

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