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Custom PC's Ultimate Core 2 Overclocking Guide
Not sure where to begin when overclocking? Alex Watson uncovers the dark art of coaxing more speed out of your PC's components for free.
The sSpec (aka the specification number) allows you to determine the stepping of the chip. In the case of the Q6600, the G0 stepping's sSpec number is SLACR, while the B3's sSpec number is SL9UM. You can check which specs accompany which sSpec numbers by using Intel's Processor Spec Finder (http://processorfinder.intel.com).
Tracking down core revisions is a perfectly logical approach to identifying which CPUs overclock well. However, it's also the case that fabs, like ourselves, have good and bad weeks, so different batches of chips will have varying levels of overclockability. News of which batches of CPUs are good overclockers is traded on forums such as our own (www.custompc.co.uk/phpbb), Extreme Prometia (www.ep-uk.co.uk/forum/index.php), Xtreme Systems (www.xtremesystems.org/forums/index.php) and Extreme Overclocking. The latter has a particularly good thread (http://forums.extremeoverclocking.com/showthread.php?t=244601), which lists the overclocks that people have achieved with their chips, along with lots of data about the processor, including the Week and Code. As with the sSpec, these are listed on the box and should enable you to research your chip choice very specifically.
Problem alert: As overclocking depends on so many factors – stepping code, batch number, the stage of the core’s life cycle – remember that your mileage may vary (YMMV) when overclocking.
How can you get more speed?
To understand how to overclock a CPU, you first need to know how a CPU's clock frequency is calculated and how this relates to the frequency of other components, such as the memory. Intel CPUs derive their speed from a combination of the front side bus (FSB) speed and clock multiplier. The FSB might sound like a Soviet secret police force, but it's actually a data link between the CPU and other components in the PC via a chip on the motherboard called a Northbridge. Popular Northbridges include Intel's P965 and P35, plus Nvidia's nForce 680i SLI. The Northbridge contains the memory controller, apart from in Athlon 64 PCs, where the controller is part of the CPU.
The faster the FSB, the more data can be communicated to and from the CPU, which is why Intel's cheapest CPUs use an 800MHz FSB, its mid-range CPUs a 1,066MHz FSB and its top-end, newest offerings a 1,333MHz FSB. However, these values are four times the actual FSB speed, owing to the fact that data can be sent four times per clock cycle, a technique Intel calls 'quad-pumping'.
