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1. Mapping Functions
A mapping function is the method used to locate a memory address
within a cache
It is used when copying a block from main memory to the cache and it is
used again when trying to retrieve data from the cache
•Cache mapping defines how a block from the main memory is
mapped to the cache memory in case of a cache miss.

2. Cache Example
These notes use an example of a cache to illustrate each of the mapping
functions. The characteristics of the cache used are:
• Size: 64 kByte
• Block size: 4 bytes – i.e. the cache has 16k (214) lines of 4 bytes
• Address bus: 24-bit– i.e., 16M bytes main memory divided into 4M 4 byte blocks
• Main memory is divided into equal size partitions called
as blocks or frames.
• Cache memory is divided into partitions having same size as that of
blocks called as lines.
• During cache mapping, block of main memory is simply copied to the
cache and the block is not actually brought from the main memory.

3. The following diagram illustrates the mapping
process-

4. Cache Mapping Techniques-
• The memory system has to quickly determine if a given address is in
the cache
• There are three popular methods of mapping addresses to cache
locations4
–Fully Associative – Search the entire cache for an address
– Direct – Each address has a specific place in the cache
–Set Associative – Each address can be in any of a small set of cache
locations