A little background…
Ranked as the 33rd largest supercomputer in the world at the time, the "Condor Cluster" was built by the U.S. Air Force Research Laboratory using 1,760 Playstation 3s. Situated in Rome, New York, the system was constructed for radar enhancement, processing satellite imagery, and researching AI.
The console was chosen for its efficiency in handling high-resolution graphics as well as its general affordability.
The "Condor Cluster" would 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).
While the PlayStation 3 was priced at around $400 at the time, it's reported that the AFRL was otherwise looking at an expense of $10,000 per unit for comparable technology built with conventional computer parts. The PS3 was also ideal for its ability to run Linux, although this feature was later removed due to security concerns, halting potential future projects of PS3-based clusters.
Prior to the AFRL's project, Gaurav Khanna at the University of Massachusetts Dartmouth physics department built a similar machine using almost 200 PlayStation 3 consoles.