Editing CPU cache (section)

===Direct-mapped cache===
In this cache organization, each location in the main memory can go in only one entry in the cache. Therefore, a direct-mapped cache can also be called a "one-way set associative" cache. It does not have a placement policy as such, since there is no choice of which cache entry's contents to evict. This means that if two locations map to the same entry, they may continually knock each other out. Although simpler, a direct-mapped cache needs to be much larger than an associative one to give comparable performance, and it is more unpredictable. Let {{mvar|x}} be block number in cache, {{mvar|y}} be block number of memory, and {{mvar|n}} be number of blocks in cache, then mapping is done with the help of the equation {{math|''x'' {{=}} ''y'' mod ''n''}}.