Core i7 860 and Core i7 920 are based on two different set of architectures (although both shares some common features and based on an architecture called Nahealem).
Core i7 920 is the big daddy and released earlier. These series of processors are termed as Intel Bloomfield. They are based on 45nm fabrication process, having Hyper threading enabled (So they can process 8 threads simultaneously), On-Die memory controller, hence removing the concept of FSB. They are compatible with Intel X58 chip-set based motherboards having 1366 pin LGA . They are having Tri-Channel memory controller and can able to access 3 memory modules simultaneously. As a result, they have a huge memory bandwidth, one of the reasons of its great performance.
Core i7 920, 930, 965 ar example of it.
Core i7 860, is on the other hand based on Intel lynnfield based micro-architecture. They are having LGA 1156 based connector and compatible with Intel P55 chip-set based motherboards.
Like their bigger brother, they also have On-Die memory controller and even having their PCI Express Graphics controller embedded in their CPU die. They support maximum of X16 bandwidth. As a result in single GPU performance they can perform better than Core i7 9XX series due to the removal of latency to access motherboard for PCI Express controller. However, they are having dual channel memory controller compared to the Triple Channel configuration of Bloomfield, but each of their memory controller are faster.
The 1st and the cheapest one from this series is Core i5 750. This one is not having Hyper Threading. However, Core i7 860 is having hyper threading enabled and that's why it is called Core i7 rather than Core i5
