Organisation of cache memory
- 2. What is Cache Memory? Cache Memory is a special very high-speed memory. It is used to speed up and synchronizing with high-speed CPU. Cache memory is costlier than main memory or disk memory. Cache Memory acts as a buffer between RAM and the CPU. Cache memory is used to reduce the average time to access data from the Main memory.
- 3. Fig. Positioning of Cache memory in computer organisation
- 4. Register Cache Memory Main Memory Secondary Memory Levels of Memory
- 5. Cache Mapping There are three different types of mapping used for the purpose of cache memory: Direct Mapping o The simplest technique, which maps each block of main memory into only one possible cache line. o Assign each memory block to a specific line in the cache. o If a line is previously taken up by a memory block ,the old block is trashed. An address space is split into two parts index field and a tag field. Direct mapping`s performance is directly proportional to the Hit ratio
- 6. Associative Mapping o To store content and addresses of the memory word. o Any block can go into any line of the cache. o Enables the placement of any word at any place in the cache memory. o Fastest and the most flexible mapping form.
- 7. Set-associative Mapping o Enhanced form of direct mapping o Addresses the problem of possible thrashing in the direct mapping method. o Instead of having exactly one line that a block can map to in the cache, it groups a few lines together creating a set. Then a block in memory can map to any one of the lines of a specific set. o Allows each word that is present in the cache can have two or more words in the main memory for the same index address.
- 8. Cache Performance Cache Hit Cache Miss If the processor finds that the memory location is in the cache, a cache hit has occurred and data is read from cache If the processor does not find the memory location in the cache, a cache miss has occurred Hit Ratio= Hit (Hit+Miss)
- 9. Spatial Locality of Reference Locality of Reference Temporal Locality of Reference