A TFLOP is one trillion floating points operations a second. I think an i7-980X does about 80 gigaFLOPS. So 13 of them would do around one TFLOP.

The best way to measure gigaFLOPS is with the Linpack benchmark.

http://software.intel.com/en-us/arti...pack-download/

There's a list of the Top-500 supercomputers. The slowest one does 20 TFLOPS. The fastest one can do 1,759 TFLOPS or 1.759 quadrillion floating point operations per second.