Dude... it's a much better Cell processor. The Cell processor is not only a Sony product.
It was developed by Toshiba, Sony and IBM. IBM is the producer of that supercomputer, using a lot more advance Cell procesors, not the ones in the PS3.
In fact, its a very modified Cell processor, called IBM PowerXCell: In May 2008, IBM introduced the high-performance double-precision floating-point version of the Cell processor, the PowerXCell 8i, at the 65 nm feature size.
But the main power comes from the AMD Processors. The PowerXCells is just to accelerate the speed.
http://en.wikipedia.org/wiki/IBM_Roadrunner
"IBM Roadrunner uses an updated version of the Cell processor, manufactured using 65 nm technology and enhanced SPUs that can handle double precision calculations in the 128-bit registers, reaching double precision 100 GFLOPs"
http://en.wikipedia.org/wiki/Cell_microprocessor#Supercomputing
