At the end of 2008 Intel released the Core i7. Aimed purely at enthusiasts, this range of CPUs took performance to a whole new level and also gifted gamers Crossfire and SLI support on a single, stable platform.

Unfortunately the technology was priced at a level that placed it beyond the reaches of the mainstream, with not only the CPUs starting at over £200, but the motherboards also costing at least twice as much as comparative Phenom and Core 2 alternatives.

Couple that to the relatively high price of triple-channel DDR3 memory kits and system integrators struggled to get the cost of a base unit below £750. With AMD finally eclipsing even the fastest Core 2 CPUs with its Phenom II X4 965, Intel could no longer leave this ageing technology to represent the mainstay of its processor fleet. Enter the solution to Intel's dilemma. Enter the Core i5...

Core i5's Lynnfield architecture is a direct evolution of the Core i7, with essentially the same chip topology minus a channel on the memory controller. Gone too is the QPI which, like AMD's Hyper Transport bus, provided an ultra-fast link to other processors and system components. This doesn't matter however, as Lynnfield gains an on-chip PCI Express controller providing an ultra-low latency link between the video card and the chip.

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The technology also gets a new socket; LGA 1156. At roughly the same size as an LGA 775 processor, socket 1156 will also support a range of 800-series Core i7 products. These differ architecturally from their Core i5 siblings in only one way; the inclusion of Hyper Threading.

Hyper Threading is a technology that allows each core to execute two threads simultaneously and can provide significant gains in performance when faced with either heavy multi-tasking, or programs that have been optimised for multiple cores.

Both socket 1156 families of chips benefit from a new and improved implementation of Intel's Turbo mode, however, which can disable idle cores and put the resulting thermal improvement to good use by heavily overclocking the active ones. Turbo mode is nothing new; Socket 1366 Core i7s also have it, but due to more extensive power saving features on idle cores, Intel is able to be much more aggressive this time around. With just one or two cores active the i5 750 can increase its multiplier all the way up to 24x, allowing for a clock speed increase of 20 percent to 3.2GHz.

Intel is also launching a new chipset along with socket 1156; the P55. This does away with the ICH10R Southbridge required by the X58 and handles storage, USB and PCIe 1x buses directly, but also lacks the ultra-wide 36-lane PCI Express capabilities of its bigger brother.

This makes the platform less well suited to high-end multi-GPU gaming configurations, but as this only makes up a small proportion of the PC market, it won't be a problem for many. The best news for mainstream users is the pricing of socket 1156 boards. Although the ludicrously expensive high-end market is still well-served, we have already seen low-cost P55 boards for around £90, which is a good £45 less than the cheapest Socket 1366 equivalents.

So, how does the cut-down yet souped-up Lynnfield perform? At 2.66GHz the entry-level i5 750 part is clocked at the same speed as the Core i7 920, and across the spectrum of our tests it provided stellar performance. In programs that make effective use of multiple cores the Hyper Threading capabilities of the 1366 part see it coming out on top (by 3-4 percent in video encoding and Photoshop respectively), but in less well-optimised applications the i5 actually has the lead thanks to its more aggressive Turbo mode implementation (1-2 percent in Sysmark 2007).

Gaming also seems to benefit as FarCry 2, Left 4 Dead and Crysis Warhead all showed small leads for the i5 (by around 1-3 percent), whilst multi-tasking is again better served by the premium i7 parts.

What's abundantly clear is that the i5 is consistently faster than the Q9650; the fastest mainstream Core 2 Quad. It's also slightly faster than the Phenom II X4 965, though not in every situation. At under £150, however it's considerably cheaper than AMD's finest, making it a much more compelling choice. Unless AMD can bring its processors in line with Intel's pricing or significantly ramp up clock speeds, it's in for another difficult quarter.

Overall the Core i5 is a superb processor. Its mission was to beef up Intel's performance in the mainstream sector whilst serving the Phenom II 965 its notice as the fastest non-i7 processor. In both objectives it has succeeded, and whilst the Core i7 is still the best option for those requiring the most threads from their CPUs, this is definitely the best choice for the majority of users looking for a new Windows 7 PC this year.