[quotemsg=11154771,0,125865][quotemsg=11154303,0,1099912]The Ivy Bridge Xeon E5s are already sporting 12 core / 24 thread. I wonder why the LGA2011 based i7s are lagging behind with still 6C/12T.[/quotemsg]
It is called market segmentation and product differentiation: Intel does not want their high-margin workstation and server customers to drop Xeons in favor of i7 so expect high-end mainstream parts to continue having 25-50% fewer cores than Xeons simply because Intel does not want the two to overlap too much.[/quotemsg]
^ This, but I think it also has a lot to do with (surprisingly) IBM, and TDP. Competition with IBM in certain server and HPC markets is driving Intel towards parallel computing and greater core counts within the same TDP, even at the expense of clock frequency. This is because the main performance factors in many of these workloads is core count and not GHz. Efficiency is also very important, so if it's a choice between an 8 core ~3.0 GHz, or a 6 core ~3.5 GHz within a 130W TDP, the choice is very clear (at least for Xeons). The same cannot be said for i7's, where competitive clock frequencies are still very important due to workloads that are typically not nearly as parallel (such as games).
LGA2011 i7's also have to compete with LGA1155/1150, and Intel doesn't want a situation where their mainstream processors completely blow away their prosumer processors in lightly threaded workloads. This is another reason they have to keep those clock frequencies up.