Intel has just recently launched some overclocker friendly CPUs, named the Core i5-655K and the Core i7-875K. These new “K”s are different because they have an unlocked multiplier, allowing increments above what is usually allowed by Intel for that class of processor.
The total CPU clock speed is determined by its fundamental bus speed, multiplied by the ‘multiplier’ factor. So for example, the 655K has a CPU clock speed of 3.2GHz, which based on its 133MHz “base clock” bus multiplied by its 24x multiplier (OK so it comes to 3192MHz, but it’s close enough). Being able to turn up the dial on the multiplier means that there are less limiting factors to the overclock: just CPU and motherboard. With other CPUs only the base clock can be turned up, which means every associated bus on the motherboard: memory, QPI and sometimes even PCI-Express also change as well. With so many other factors changing, it takes just one weak link to limit your overclocking potential. By turning up the multiplier, the CPU itself is the central and almost only focus.
Intel Core i5 CPU
I say almost, because any overclock requires extra cooling: be it a heatsink and fan, or watercooling or even professional phase-change for sub-zero temps; and also a solid motherboard capable of providing plenty of nice, clean power.
The ASUS Republic of Gamer motherboards are perfect for this: the Maximus and Extreme have plenty of power phases and super-high capacity ML-caps to provide the reliable source of power that overclocking demands. If you can’t quite afford the black and red boards, the black and blue P7P55D Deluxe, EVO or P7H57D-V EVO offer much the same core engineering pedigree, but without the high-cost Fujitsu ML-capacitors or more extensive cooling.
The CPU multiplier adjustment option in ASUS P7P Motherboard BIOS
While the Core i5-655K retails for a bit more than its i5-650 brother, it’s still great value at just $176, but it’s the Core i7-875K that is actually $220 cheaper than the i7-870 that looks like the one to buy. The full-fat 4 core, 8 thread i7-875K CPU gives even LGA1366 Core i7s a run for their money, as the whole P55 platform is generally better value than an X58 and also overclocks slightly more to boot!