Xeon 3400-series processors based on Lynnfield fill the gap between the previous 3300-series "Yorkfield" processors and the newer 3500-series "Bloomfield". Like Bloomfield, they are quad-core single-package processors based on the Nehalem microarchitecture, but were introduced almost a year later, in September 2009. The same processors are marketed for mid-range to high-end desktops systems as Core i5 and Core i7. They have two integrated memory channels as well as PCI Express and Direct Media Interface links, but no QuickPathInterface.
Here you can see a comparison of all Lynnfield processors:
You'll see that key difference between a Xeon and Core i5/i7 processor is support for ECC memory, as Xeon is targeted for servers.