At around $500 a pop, Nvidia's dual-GPU GeForce 9800 GX2 graphics card may be a little too pricey for most gamers to afford. However, scientists at the University of Antwerp in Belgium think it's a pretty good building block for desktop supercomputing. The ASTRA research group at the University's Vision Lab has built a desktop system with four GeForce 9800 GX2 graphics cards, which it uses for tomography computations. In ASTRA's words, tomography "is a technique used in medical scanners to create three-dimensional images of the internal organs of patients, based on a large number of X-ray photos that are acquired over a range of angles." With the computing power of four 9800 GX2s, ASTRA says it can perform tomography calculations at the same rate as 350 modern microprocessor cores all working together. That can cut computing times from weeks on a regular PC to just a few hours. Building the machine cost a total of less than 4,000 euros ($6,200), which is at least a couple orders of magnitude cheaper than a conventional server cluster. (thanks TechReport)