How Much Bigger A Cache Can Be Used?

Cache is usually referred by two words that are "small enough" and large enough". The small enough means, its cost per bit is less in contrast to RAM, while by large enough means, its access time is good, means there is no need to have the huge amount of data in the cache but it works like the RAM, means it have the desired data always. So there is no need of large capacity.

If the cache size is big then there will be more chances of successful hits, and hit ratio will be more. cache size should not be grow up-to very high level, it must be up-to some specific point, when size of the cache is move beyond that point, then cache would not be able to achieve the good performance, because searching will take so much time. It means that if the size of the cache is very large then cache will not be a cache any more, it will become RAM, which has all the data, but its performance is degraded because of searching. So the cache size should be at some optimal level means cache size should be fix up-to some extent size.