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.
Mac Pro
The 2009 and later Mac Pro systems were available with one or two central processing units (CPU) with options giving four, six, eight, or twelve cores. As an example, the eight core standard configuration Mac Pro uses two Quad core ×8 Intel E5620 Xeon CPUs at 2.4 GHz, but could be configured with two Hexa Core Intel Xeon X5670 CPUs at 2.93 GHz. The 2008-2009 model CPUs use the LGA 771 socket, while the 2010 and later use the LGA 1366 socket, meaning either can be removed and replaced with compatible 64-bit Intel Xeon CPUs; however, it should be noted that as a 64-bit EFI firmware was not introduced until the MacPro3,1, earlier models can only operate as 32-bit despite having 64-bit Xeon processors. The newer LGA 1366 sockets utilize Intel's QuickPath Interconnect (QPI) integrated into the CPU in lieu of an independent system bus; this means the "bus" frequency is relative to the CPU chipset, and upgrading a CPU is not bottlenecked by the computer's existing architecture.