Xeon

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)[1].

Pentium III Xeon
In 1999, the Pentium II Xeon was replaced by the Pentium III Xeon. Reflecting the incremental changes from the Pentium II "Deschutes" core to the Pentium III "Katmai" core, the first Pentium III Xeon, named "Tanner", was just like its predecessor except for the addition of Streaming SIMD Extensions (SSE) and a few cache controller improvements. The second version, named "Cascades", was based on the Pentium III "Coppermine" core. The "Cascades" Xeon used a 133 MT/s bus and relatively small 256 KB on-die L2 cache resulting in almost the same capabilities as the Slot 1 Coppermine processors, which were capable of dual-processor operation but not quad-processor operation. To improve this situation, Intel released another version, officially also named "Cascades", but often referred to as "Cascades 2 MB". That came in two variants: with 1 MB or 2 MB of L2 cache. Its bus speed was fixed at 100 MT/s, though in practice the cache was able to offset this. Product codes for Tanner and Cascades mirrored that of Katmai and Coppermine; 80525 and 80526 respectively.

Xeon (DP) & Xeon MP (32-bit)
Foster
In mid-2001, the Xeon brand was introduced ("Pentium" was dropped from the name). The initial variant that used the new NetBurst architecture, "Foster", was slightly different from the desktop Pentium 4 ("Willamette"). It was a decent chip for workstations, but for server applications it was almost always outperformed by the older Cascades 2 MB core and AMD's Athlon MP. Combined with the need to use expensive Rambus Dynamic RAM, the Foster's sales were somewhat unimpressive.

At most two Foster processors could be accommodated in a symmetric multiprocessing (SMP) system built with a mainstream chipset, so a second version (Foster MP) was introduced with a 1 MB L3 cache and the Jackson Hyper-Threading capacity. This improved performance slightly, but not enough to lift it out of third place. It was also priced much higher than the dual-processor (DP) versions. The Foster shared the 80528 product code with Willamette.