Blue Gene/P will be capable of a peak performance of 3000 trillion calculations, or floating point operations, per second (3 petaflops). But its sustained performance is expected to level out at around 1 petaflop.
Each processing chip inside the machines contains 4 unique processor cores. There are 32 of these processors in every circuit board, and 32 circuit boards in every rack. With a total of 216 racks, the full machine features 884,736 unique processor cores.
The first Blue Gene/P machine will be installed at the US Department of Energy's Argonne National Laboratory in Chicago, US, later in 2007. It will be used primarily to perform nuclear weapons simulations at that laboratory. Other systems will then be installed in Germany, the UK and elsewhere in the US.
I don't work on Blue Gene, but there are folks in my building who do, so I have take vicarious pride in the accomplishment. Congratulations, Blue Gene team!