NehalemCalc

Armed with QuickPath Interconnect, Intel’s new Core i7 CPU has a whole suite of multipliers and frequencies that make overclocking more complicated than ever. To keep track of the dizzying array of clockspeeds and multipliers,NehalemCalc will do the number-crunching for you.
BClock
With the adoption of QuickPath Interconnect, the traditional model of the frontside bus has been abandoned in favor of the BClock. Where the FSB frequency once help set the speed for the CPU and the memory, the new BClock helps set the CPU, DRAM, L3 cache, memory controller, and system bus frequencies.
QPI
Now that the FSB is out the door, the Nehalem platform is rigged with a high-speed bi-directional system bus. This QPI bus runs on an independent frequency and uses its own set of multipliers. Altering this frequency can substantially impact the speed at which add-in cards and peripherals transfer data on a Nehalem platform.
Uncore
Yet another new and independent frequency with its own set of multipliers. The uncore frequency sets the speed of both the Nehalem’s on-die memory controller and the L3 cache
Memory Multiplier
Memory has definitely changed with the release of the Nehalem. Rather than using memory dividers to set the clockspeed of the DRAM, the DRAM’s speed is now derived from the BClock with a multiplier. This multiplier must be less than half that of the Uncore’s multiplier.
CPU
Doing away with paltry multipliers like 6x, the Core i7 uses multipliers of up to 25x in multiplying the BClock to generate the CPU’s frequency.