The Xeon brand refers to many families of Intel's x86 multiprocessing CPUs – for dual-processor (DP) and multi-processor (MP) configuration on a single motherboard targeted at non-consumer markets of server and workstation computers, and also at blade servers and embedded systems. The Xeon brand has been maintained over several generations of x86 and x86-64 processors. Older models added the Xeon moniker to the end of the name of their corresponding desktop processor, but more recent models used the name Xeon on its own. The Xeon CPUs generally have more cache than their desktop counterparts in addition to multiprocessing capabilities. Intel's (non-x86) IA-64 processors are called Itanium, not Xeon.
Pentium II Xeon:
The first Xeon branded processor was released in 1998, named the Pentium II Xeon (codenamed "Drake"), as the replacement of the Pentium Pro. It was based on the 0.25 µm "Deschutes" core (P6 microarchitecture) branded Pentium II (sharing its 80523 product code), used either a 440GX (a dual-processor workstation chipset) or 450NX (quad-processor, or oct with additional logic) chipset, and differed from the Pentium II desktop CPU (Deschutes) in that its off-die L2 cache ran at full speed. It also used a larger slot known as slot 2. Cache sizes were 512 KB, 1 MB, and 2 MB, and it used a 100 MT/s front side bus (FSB) .