typical cache size

typical 486 computer like the "wearcomp" in ece385 has 8k of L1 cache, and 0k of L2 cache.

many low power (battery operated) computers have zero L2 cache in order to reduce power consumption.

cache levels: hierarchy

previously lectures covered caches (L1).

now we proceed further down the memory hierarchy.

second level caches

performance gap between CPUs and memory leads to a choice between making the cache faster (to keep pace with the CPU) or bigger (to keep pace with main memory, e.g. to reduce misses).

should we make the cache faster or bigger?

one possible answer is both.

L1 cache small and therefore fast enough to be clocked at same speed as CPU.

L2 cache big enough to get many accesses that would otherwise go to main memory.

L2 cache reduces the miss penalty when something is not found in L1 cache.