As noted by AppleInsider, the University of Illinois has implemented a 640-node Xserve G5 cluster called the Turing Cluster. The project is operated by the schoolis Computational Science and Engineering Graduate Option Program, and was provided by Apple to the school "under a combination purchase/donation agreement."
The Turing Cluster is available to students and faculty for school-related projects. The schoolis Usage Policies specify that "the cluster is to be used for scientific and engineering computational jobs only; no other work is allowed." In addition, sponsors of the program, all different departments in schools in the University of Illinois, can utilize the system for their own projects.
The cluster uses 640 dual 2GHz Xserves, for a total of 1280 processors, each with 4 gigabytes of RAM. The Xserves are installed in 19 racks, each with 32 to 35 Xserves. For storage, the Turing Cluster uses two Xserve RAIDs for a total of seven terabytes of storage.
The Turing Cluster joins other notable Xserve clusters such as System X at Virginia Tech and a cluster of 1,566 Xserves for the US Army. Apple is a new player to the High Performance Computing market, but has made substantial inroads with the Xserve, Xserve RAID, Xgrid, and Xsan.
A picture of the Turing Cluster from University of Illinois Web site.
The University of Illinois has posted a photo gallery of the project, showing it at various stages of development. You can also see a rather blurry, but live image of the cluster through the Turing Cluster Webcam.
AppleInsideris coverage includes additional information about the move to Mac OS X, and other related information.