FSB Bottleneck contd….
•F is application dependent. For lattice calculations it is around 1.
•When B/F >> P, P determines the performance.
•When B/F << P, maximum sustained performance is B/F independent of P!
•Example: For Xeon with 400 Mhz FSB, maximum B is 3.2 GB/s. If F =2, B/F is 1.6 GFLOPs. Even if it is a 8 Ghz CPU, this is all that one can get!