sector mapping

In this scheme the memory and cache are divided into blocks

of 2^m bytes (the cache line size). A sector consists of

2^n consecutive blocks.

When a block is cached, it is read into the correct position

in any sector of the cache, given by discarding the bottom m

address bits and taking the next n as the block number within

the sector.

That whole sector is then tagged with the remaining upper

address bits and the other blocks in the sector are marked as

invalid. This scheme takes advantage of locality of reference

to consecutive blocks and needs fewer tags thus reducing the

cost of associative access to the tags.