Direct mapping cache pdf

In this a given main memory block can be placed in one and. The tasks required of the direct mapped cache in servicing a memory request. For a direct mapped cache with 2n blocks, n bits are used for the index. Memory locations 0, 4, 8 and 12 all map to cache block 0. Each memory block is mapped to exactly one slot in the cache directmapped. Table of contents ii multilevel caches unified versus split caches. Draw the cache and show the final contents of the cache as always, show your work. For example, on the right is a 16byte main memory and a 4byte cache four 1byte blocks. Direct mapped eheac h memory bl kblock is mapped to exactly one bl kblock in the cache lots of lower level blocks must share blocks in the cache address mapping to answer q2. In direct mapping, a particular block of main memory can be mapped to one particular cache line only. Consider a direct mapped cache of size 64k with block size of 16 bytes. Direct mapping map cache and main memory break the. Adapted from computer organization and design, 4thedition, patterson and hennessy. Pdf improving directmapped cache performance by the addition.

Cache addresses cache size mapping function direct mapping associative mapping setassociative mapping replacement algorithms write policy line size number of caches luis tarrataca chapter 4 cache memory 3 159. Directmapped and set associative caches eecs instructional. By reducing number of possible mm blocks that map to a cache block, hit logic searches can be done faster. Pdf hardware techniques for improving the performance of caches are presented. Intermediate level between cpu and memory inbetween in size, cost, and speed memory hierarchy, organization, structures set up to exploit temporal and spatial locality. Directmapped caches, set associative caches, cache. Directmapped caches each memory block is mapped to exactly one slot in the cache directmapped every block has only one home use hash function to determine which slot comparison with fully associative check just one slot for a block faster.

Directmapped caches, set associative caches, cache performance. Block j of main memory will map to line number j mod number of cache lines of the cache. A direct mapped cache has one block in each set, so it is organized into s b sets. Following diagram shows how the address is divided. If the valid bit for that block location is gated 2, then that tag is gated out, 3. No replacement policy necessary access pattern may leave empty slots in. For each address, compute the index and label each one hit or miss 3. Chapter 4 cache memory computer organization and architecture. Direct mapped cache an overview sciencedirect topics. Miss caching places a small, fully associative cache between a cache. Direct mapping address structure tag line or slot word t s w cache line size determines how many bits in word field ex. Write the appropriate formula below filled in for value of n, etc. An address in block 0 of main memory maps to set 0 of the cache. To understand the mapping of memory addresses onto cache blocks, imagine main memory as being mapped into bword blocks, just as the cache is.

You will calculate the miss rate for the following code using this cache. How many bits are in the tag, line and offset fields. In this article, we will discuss practice problems based on direct mapping. Mapping function direct, assoociative, set associative. Direct mapping cache practice problems gate vidyalay.