In Figure Q1.2 the performance of a 4 Kbyte cache is plotted against the number of ways of associativity from 1 (direct mapped) to 256 (fully associative). The cache line length is 16 bytes. Also shown is the external memory bandwidth. Why does the external memory bandwidth decrease as the ways of associativity increases?

Relative performance 2.5 DE DEDE BORSABB L performance external memory bandwidth 1248' 16' 32'64 128 256 associativity (ways) Figure 01.2