Xeon
Introduced in May 2013, Xeon E3-12xx v3 is the first Xeon series based on the Haswell microarchitecture. It uses the new LGA 1150 socket, which was introduced with the desktop Core i5/i7 Haswell processors, incompatible with the LGA 1155 that was used in Xeon E3 and E3 v2. As before, the main difference between the desktop and server versions is added support for ECC memory in the Xeon-branded parts. The main benefit of the new microarchitecture is better power efficiency.
Xeon
The first dual-core CPU branded Xeon, codenamed Paxville DP, product code 80551, was released by Intel on October 10, 2005. Paxville DP had NetBurst microarchitecture, and was a dual-core equivalent of the single-core Irwindale (related to the Pentium D branded "Smithfield") with 4 MB of L2 Cache (2 MB per core). The only Paxville DP model released ran at 2.8 GHz, featured an 800 MT/s front side bus, and was produced using a 90 nm process.