Xeon
The first Xeon-branded processor was the Pentium II Xeon (code-named "Drake"). It was released in 1998, replacing the Pentium Pro in Intel's server lineup. The Pentium II Xeon was a ""Deschutes"" Pentium II (and shared the same product code: 80523) with a full-speed 512 kB, 1 MB, or 2 MB L2 cache. The L2 cache was implemented with custom 512 kB SRAMs developed by Intel. The number of SRAMs depended on the amount of cache. A 512 kB configuration required one SRAM, a 1 MB configuration: two SRAMs, and a 2 MB configuration: four SRAMs on both sides of the PCB. Each SRAM was a 12.90 mm by 17.23 mm (222.21 mm²) die fabricated in a 0.35 µm four-layer metal CMOS process and packaged in a cavity-down wire-bonded land grid array (LGA). The additional cache required a larger module and thus the Pentium II Xeon used a larger slot, Slot 2. It was supported by the 440GX dual-processor workstation chipset and the 450NX quad- or octo-processor chipset.
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.