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!