Where does all the computer power go?

According to The Economist:

Last year an IBM supercomputer called Roadrunner, based at the Los Alamos National Laboratory in New Mexico, established a new record by operating at more than one petaflop (1,000 trillion calculations a second). Roadrunner is the world’s first “hybrid” supercomputer, having been assembled in part from off-the-shelf equipment, including 12,960 Cell processor chips like those found inside the PS3. It will be used to simulate the behaviour of nuclear weapons.

The Economist, in another related article about a new virtual autopsy system states:

The body needing to be examined is first scanned using a computed tomography (CT) machine, a process which takes about 20 seconds and creates up to 25,000 images, each one a slice through the body. Different tissues, bodily substances and foreign objects (such as bullets) absorb the scanner’s X-rays in varying amounts. The software recognises these and assigns them a density value. These densities are then rendered with the aid of an NVIDiA graphics card, of a type used for high-speed gaming, into a 3-D visualisation of different colours and opacities. Air pockets are shown as blue, soft tissues as beige, blood vessels as red and bone as white. A pathologist can then peel through layers of virtual skin and muscle with the click of a computer mouse.

To make the process easier, Dr Persson and his colleagues have also created a virtual autopsy table. This is a large touch-sensitive LCD screen which stands like a table in an operating room, displaying an image of the body. Up to six people can gather around the table and, with a swipe of a finger, remove layers of muscle, zoom in and out of organs and slice through tissue with a virtual knife.