Why an L2 Cache?
The cache hit/miss ratio, and therefore overall system performance, is determined by several factors (see below). One of the crucial factors is the ratio between the size of the cache and the size of system RAM. As previously noted, L1 caches are generally 8kb-16kb in size. This tiny cache is not sufficient to produce a large cache hit/miss ratio with any significant amount of system RAM. Therefore, performance suffers significantly without an L2 cache. It is not uncommon, for example, for a 486 system with an efficient L2 cache to far outperform a Pentium system without a cache. In a recent industry magazine test of notebook computers, a 486 machine (with L2 cache) outperformed a Pentium 90 machine (without L2 cache) by 30%. L2 cache sizes range from 64K-1024K, with 256K being by far the most common size. More on L2 cache sizing later. Cache Performance Considerations [The following factors influence the performance of a cached system:] Cache Controller Design Efficiency All caches ar
