The Next Bus step
Intel's latest series of CPUs come to us with a new numbering system. They have been given the 6x40 and 6x50 branding. any CPU with the 6x40 or 6x50 tags are 1333Mhz FSB rated CPUs. Intel has moved its high-end Extreme, Quad core and Duo series to the 1333Mhz FSB series. The E4xxx are not moving past their 800Mhz FSB rating allowing Intel to keep the price of the CPU as low as possible, as well as crippling its raw speed compared to the 1066MHz series.
The biggest thing is the Core 2 Quad CPU which will in theory benefit from the increased FSB speed compared to that of the standard Core 2 Duo series. Why you may ask? Simply put, Intel's Core 2 Quad puts two Core 2 Duo CPUs on a single CPU package, the two cores are separate and have no direct access to each other. For inter-core communications between the two separate dies, it has to go along the traditional FSB, this is identical to how the old SMP setups used to work (like the Pentium III) in dual CPU configurations.
A single Core 2 CPU can chew up significant amounts of bandwidth quite easily on its own, when it has to contend with another CPU wanting access it's all up to how fast you can feed the cores, and the 1333MHz FSB can give quite a bit more bandwidth which obviously allows the transfer to happen much quicker.
Intel's platform of choice for the 1333MHz FSB CPU is the P35, this being the newest kid on the block. Intel's P35 chipset manages to run speeds of 1333MHz without any problems, not only this but it also packs a DDR-III memory controller for higher speed memory and greater bandwidth, something the Core 2 Quad really needs. Until Intel releases a true Quad Core CPU, the faster the bus you can get the better off you're going to be.