Xserve

Xserve is the name of Apple Inc.'s 1U rackmount line of server computers. When the Xserve was introduced in 2002, it was Apple's first designated server hardware design since the Apple Network Servers of 1996. It initially featured one or two PowerPC G4 processors, but was later switched over to the new PowerPC G5, and now runs on two dual-core Xeon CPUs. The Xserve can be used for a variety of applications, including file server, web server or even high-performance computing applications using clustering - a dedicated cluster Xserve, the Xserve Cluster Node, without a video card and optical drives is also available. If additional hard disk space is needed, its companion external RAID array Xserve RAID can be connected to it via Fibre Channel.
See more at Wikipedia.org...