So besides the 750 model being quad core, there is completely different architecture involved. i.e. the way i5 and the motherboard and ram are linked on socket LGA1156 compared to the socket 775 motherboard and chips.
Check out the block diagrams on the intel site for the t6600 compared to any of the i5s. There is no longer an FSB and the mem is directly connected to the processor along with the primary PCIe.
Sorry didnt cop it was a mobile processor. Here's a similar i5 mobile processor for comparison
http://ark.intel.com/Product.aspx?id=43537&code=Intel%c2%ae+Core%e2%84%a2+i5-430M+Processor+(3M+Cache%2c+2.26+GHz)