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.
Xeon
The 3000 series, codenamed Conroe (product code 80557) dual-core Xeon (branded) CPU, released at the end of September 2006, was the first Xeon for single-CPU operation. The same processor is branded as Core 2 Duo or as Pentium Dual-Core and Celeron, with varying features disabled.
They use LGA 775 (Socket T), operate on a 1066 MHz front-side bus, support Enhanced Intel SpeedStep Technology and Intel Virtualization Technology but do not support Hyper-Threading. Conroe Processors with a number ending in "5" have a 1333 MT/s FSB.The 3100 series, codenamed Wolfdale (product code 80570) dual-core Xeon (branded) CPU, was just a rebranded version of the Intel's mainstream Core 2 Duo E7000/E8000 and Pentium Dual-Core E5000 processors, featuring the same 45 nm process and 6 MB of L2 cache. Unlike most Xeon processors, they only support single-CPU operation. They use LGA 775 (Socket T), operate on a 1333 MHz front-side bus, support Enhanced Intel SpeedStep Technology and Intel Virtualization Technology but do not support Hyper-Threading.