Differences between Intel core i7 920 and Intel core i7 975 extreme cpu

I'm planning to build up my own pc. For that i have almost all the parts chosen but i want to get one of the core i7 cpu. I'm little bit confused between Intel core i7 920 and Intel core i7 975 extreme cpu. I can wait little longer and get the core i7 975 extreme which has a clock speed of 3.33Ghz and the 920 @ 2,66Ghz. But i would like to know the actual differences between Intel core i7 920 and Intel core i7 975 extreme cpu? Does any body knows about it? Kindly provide me the correct information on the above topic. Any help you can provide would be greatly appreciated. Thanks.

Core i7-975 Extreme and Core i7-920 are not in the same category. The i7-975, specifically, is for the enthusiast who wants a guaranteed 3.3 GHz+ clock rate. It’s Intel’s new top of the line desktop CPU with some modifications that may benefit you if you’ve been holding out for a faster, more efficient processor.

The 975 clocks in at 3.33 GHz sporting the same 1333 MHz Front Side Bus as all i7s. The only differences are that i7 975 is 666MHz faster and its QPI operates at 6.4GT/s instead of 4.8GT/s on the 920. Otherwise they are the same. The processor’s Intel Quick Path Interconnect (QPI) speed is still capable of producing a whopping 6.5 GT/s (not GB/s) which equates in to a very large amount of memory bandwidth. That’s 1.7 GT/s more than the base non-Extreme i7 series like the 920, 940, and 950.

The Intel Core i7 series consisted of just three processors, the Core i7-965 Extreme Edition, i7-940, and i7-920. The clear choice for the value-conscious enthusiast lies with the Core i7 920, as it overclocks, with basic air-cooling, to 3.6GHz-plus, intimating that the underlying Nehalem architecture has plenty of headroom. Knowing all this, Intel has taken its time to bolster the line-up with another chip, this time running at 3.33GHz.