There are three main methods to map main memory addresses to cache memory addresses: direct mapping, associative mapping, and set-associative mapping. Direct mapping is the simplest but least flexible method, while associative mapping is most flexible but also slowest. Set-associative mapping combines aspects of the other two methods, dividing the cache into sets with multiple lines to gain efficiency while remaining reasonably flexible.

2. There are three commonly used methods to
translate main memory addresses to cache
memory addresses.
• Direct-Mapping
• Associative Mapping
• Set-Associative Mapping

3. Fixed sized packet of information that
moves back and forth between a cache
and main memory.
Container in a cache that stores a
block as well as other information such as the
valid bit and tag bits.
Collection of one or more lines.

4. o Set of Blocks of main
memory mapped onto
specific block of
cache

5. • Cache of 64kByte.
• Cache block of 4 bytes.
• 16MBytes main memory.
• Show hexadecimal main memory
address BBBBBB in direct format.

6. • The tag memory is much smaller than in
associative mapped cache.
• It is less costly compare to other
mapping technique.
• It is easy to implement.
• It is not flexible.

7. o Any main memory blocks
can be mapped into
each cache slot.

8. • Cache of 64kByte.
• Cache block of 4 bytes.
• 16MBytes main memory.
• Show hexadecimal main memory
address BBBBBB in associate format.

9. • Flexibility. Main Memory block can be
mapped anywhere in Cache Memory.
• Regardless of how irregular the data and
program references are, if a slot is
available for the block, it can be stored in
the cache.
• Slow or expensive.

10. o Combines the simplicity of
direct mapping with the
flexibility of associative
mapping.
o Cache is divided into a
number of sets.
o Each set contains a number
of lines.

11. • 2-way set-associative.
• Cache of 64kByte.
• Cache block of 4 bytes.
• 16MBytes main memory.
• Show hexadecimal main memory
address BBBBBB in set-associate
format.

12. • Minimize the over-head in Direct and
Associate mapping.
• In our example the tag memory increases
only slightly from the direct mapping and
only two tags need to be searched for
each memory reference.
• The set-associative cache is widely used
in today’s microprocessors.

13. • Least Recently used (LRU)
e.g. in 2 way set associative Which of the 2
block is LRU?
• First in first out (FIFO)
replace block that has been in cache longest
• Least frequently used
replace block which has had fewest hits
• Random