Question

Explain why 2 cache memories are often used, and why cache I is on the same chip as the CPU.

Answer 1

2 types of cache memory : L1 cache and L2 cache

L1 cache: is extremely fast but is small and is placed on processor chip on CPU

L2 cache: it is slow than L1 cache but is big compared to it. it has high speed alternative system bus connecting it with cpu hence it doesn't get slow by the traffic on system bus.

when ever cpu searching for a data it starts searching with L1 cache which is high speed and then goes to L2 cache and then through system bus to memory. Both L1 and L2 Cache increases speed of cpu. L1 cache is limited in size due to cost factor. l2 cache is cheaper compared to l1 and is of larger size compared to it increases scope of storing more data. hence , we you two cache memories. ex: for 3 misses in L1 cache there may be only miss in L2 cache. the L1 cache has 1ns access latency while L2 cache has 10ns access latency.

L1 cache is place on processor chips of cpu itself to access data without using system bus. The speed of bus is much slower than cache hence by skipping it we access speed of nanoseconds.