PlayStation 3 cluster

The considerable computing capability of the PlayStation 3's Cell microprocessors has raised interest in using multiple, networked PS3s for various tasks that require affordable high-performance computing.
PS3 clusters.
The National Center for Supercomputing Applications had already built a cluster based on the PlayStation 2. Terra Soft Solutions has a version of Yellow Dog Linux for the PlayStation 3, and sells PS3s with Linux pre-installed, in single units, and 8 and 32 node clusters. In addition, RapidMind is pushing their stream programming package for the PS3.
On January 3, 2007, Dr. Frank Mueller, Associate Professor of Computer Science at North Carolina State University, clustered 8 PS3s. Mueller commented that the 256 MB of system RAM is a limitation for this particular application, and is considering attempting to retrofit more RAM. Software includes: Fedora Core 5 Linux ppc64,
MPICH2, OpenMP v2.5, GNU Compiler Collection and CellSDK 1.1.
In summer 2007, Gaurav Khanna, a professor in the Physics Department of the University of Massachusetts Dartmouth independently built a message-passing based cluster using 8 PS3s running Fedora Linux. This cluster was built with support from Sony Computer Entertainment and was the first such cluster that generated published scientific results. Dubbed as the "PS3 Gravity Grid", this PS3 cluster performs astrophysical simulations of large supermassive black holes capturing smaller compact objects. Khanna claims that the cluster's performance exceeds that of a 100+ Intel Xeon core based traditional Linux cluster on his simulations. The PS3 Gravity Grid gathered significant media attention through 2007, 2008, 2009 and 2010. Khanna also created a DIY website on how to build such clusters, accessible to the general public.
In November 2010 the Air Force Research Laboratory created a powerful supercomputer, nicknamed the "Condor Cluster," by connecting together 1,760 Sony PS3s which include 168 separate graphical processing units and 84 coordinating servers in a parallel array capable of performing 500 trillion floating-point operations per second (500 TFLOPS). As built the Condor Cluster was the 33rd largest supercomputer in the world and would be used to analyze high definition satellite imagery.
Single PS3.
Even a single PS3 can be used to significantly accelerate some computations. Marc Stevens, Arjen K. Lenstra, and Benne de Weger have demonstrated using a single PS3 to perform an MD5 bruteforce in a few hours. They say:
"Essentially, a single PlayStation 3 performs like a cluster of 30 PCs at the price of only one" (in November 2007). 
Medical research.
On March 22, 2007, SCE and Stanford University expanded the Folding@home project to the PS3. Along with thousands of PCs already joined over the Internet, PS3 owners are able to lend the computing power of their game systems to the study of improper protein folding and associated diseases, such as Alzheimer's, Parkinson's, Huntington's, cystic fibrosis, and several forms of cancer. The software was included as part of the 1.6 firmware update (March 22, 2007), and can be set to run manually or automatically when the PS3 is idle through the Cross Media Bar. The processed information is then sent back to project's central servers over the Internet. Processing power from PS3 users is greatly contributing to the Folding@home project, and PS3s are third to both NVIDIA and AMD GPUs in terms of teraflops contributed. As of March 2011, more than a million PS3 owners have allowed the Folding@home software to be run on their systems, with over 27,000 currently active, for a total of 8.1 petaFLOPS. By comparison, the world's most powerful supercomputer as of November 2010, the Tianhe-IA has a peak performance of 2.56 petaFLOPS, or 2,566 teraFLOPS.
The latest report stated that Folding@Home has passed the 5 native petaFLOP mark, of which 767 teraFLOPS are supplied by PlayStation 3 clients.
The Computational Biochemistry and Biophysics Lab in Barcelona has launched a distributed computing project called PS3GRID. This project is expected to run sixteen times faster than an equivalent project on a standard PC. Like most distributed computing projects, it is designed to run only when the computer is idle.
eHiTS Lightning is the first virtual screening and molecular docking software for the PS3. It was released by SimBioSys. as reported by Bio-IT World in July 2008. This application runs up to 30x faster on a single PS3 than on a regular single CPU PC, and it also runs on PS3 clusters, achieving screening of huge chemical compound libraries in a matter of hours or days rather than weeks, which used to be the standard expectation.
The decline of the PS3 cluster.
On March 28, 2010, Sony announced it would be disabling the ability to run other operating systems with the v3.21 update due to security concerns about OtherOS. This update would not affect any existing supercomputing clusters, due to the fact that they are not connected to PSN and would not be forced to update. However, it would make replacing the individual consoles that compose the clusters very difficult if not impossible, since any newer models with the v3.21 or higher would not support Linux installation directly. This caused the end of the PS3's common use for clustered computing, though there are projects like "The Condor" that were still being created with older PS3 units, and have come online after the April 1, 2010 update was released.
It is possible that a workaround might be to replace the damaged TSOP on older (ie PS3 fat) consoles with non-fatal hardware failures such as defective shaders or YLOD combined with an X-ray and BGA rework of affected memory chips. This would be acceptable for some applications as in principle it would then be custom hardware under the DMCA and not classed as reverse engineering. Additional modifications would include upgrading the thermal profile (ie larger fan/more voltage) and replacing TSOP completely with a socket so any surplus 256MB SD card can be installed in its place as some hackers have already done for development purposes only.