|Intel Core i5-661 Processor BX80616I5661|
|Reviews - Featured Reviews: Processors|
|Written by David Ramsey|
|Tuesday, 16 February 2010|
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Closer Look: Intel Core i5-661
Intel's new processors mark the company's first foray into 32nm manufacturing. Intel CPU development proceeds on what the company calls a "tick-tock" cycle: the "tick" cycle is where an existing processor architecture is refined, which means "Intel delivers new silicon process technology, dramatically increasing transistor density while enhancing performance and energy efficiency within a smaller, more refined version of our existing microarchitecture." The "tock" cycle, on the other hand, is when "Intel delivers entirely new processor microarchitecture to optimize the value of the increased number of transistors and technology updates now available." Thus, the new 2010 Intel Core Processor Family of which the Core i5-661 BX80616I5661 is a member is part of a "tick" cycle.
The cache architecture is standard for Core i5 processors: each core gets 32K of data cache, 32K of instruction cache, and 256K of Level 2 cache. 4M of Level 3 cache is shared between the two cores. These are the same specs as the Core i5-750, with the exception that the latter has twice as much shared cache, with 8M available. Of course, the i5-750 has twice as many cores as well, but the shared Level 3 cache isn't apportioned equally between the cores; depending on the load, one or two cores can use most of the cache.
Depending upon the processor load and temperature, the i5-661's clock multiplier can be varied between 9 and 25, resulting in clock speeds ranging from a mere 1.2GHz to the processor's rated speed of 3.33GHz. This feature can result in dramatically reduced power consumption when the computer is idle or performing lightweight tasks. Just sitting at the Windows desktop, the processor speed can drop to as low as 1.2GHz.
Like the previous Core i5 processors, the Core i5-661 implements Intel's "Turbo Boost", an automatic overclocking feature that can raise the frequency of one or both cores to provide better performance when the processor is not fully loaded. If only one core is in use, the multiplier can be raised to 27, resulting in a clock speed of 3.6GHz.
However, when both cores are loaded, the multiplier can only be raised to 26. The level of Turbo Boost used in the Core i5-661 is less aggressive than that used in earlier members of the family such as the Core i5-750.
The Intel Core i5-661 is one of the first CPUs Intel has produced with an integrated GPU or "iGPU". This is a separate chip, produced on the older 45nm process, that's bonded to the CPU package. In the image below, the iGPU is the lower chip in the package.
Technically known as the "GMA HD", the Core i5-661's GPU comprises an additional 177 million transistors and is an evolution of previous generations of Intels "Graphic Media Accelerator" GPUs, which remain a common feature of existing Intel motherboard chipsets. Based on previous GMA experiences, Benchmark Reviews doesn't expect much of this chip in the way of gaming performance. You cannot use the 661's integrated GPU in combination with another graphics card to run two monitors: plugging a card into your motherboard's PCI-E x16 slot automatically disables the built-in GPU. But you can run two monitors from the iGPU if your motherboard has multiple monitor connectors. The iGPU can be configured to use 32M, 64M, or 128M of your system memory as a frame buffer.
With the original Core i5/i7 CPUs, Intel moved the memory controller and PCI Express lanes off the motherboard chipset and onto the processor, resulting in reduced latencies and improved performance. These functions have been moved to the iGPU on the Core i5-661. Two other new features of the Core i5-661 are the ability to use error-correcting memory (ECC) and several new processor instructions designed to accelerate Advanced Encryption Standard (AES) operations.