Thursday, October 13, 2005
Cache memory
1. What is cache memory?
Cache memory is the fastest in memory hierarchy, which contain the in formations and instructions which are most frequently reference and currently in execution
2. What is locality of reference?
The reference of memory at a given interval of time is confined within a few localized areas in memory. This phenomenon is the property of locality of reference
3. Define cache hit.
When CPU tries to access a word, and if the referenced word is found in cache, it is cache hit
4. Define Cache miss
If the CPU is not able to find a word in cache, and it check in main memory, it is called cache miss
5. Define hit ratio
The ratio of number of cache hits to the total number of references
6. Define miss ratio
The ratio of number of cache misses to the total number of references
7. Define mapping
The transformation of data from main memory to cache memory is mapping
There are 3 types of mapping
i) Associative Mapping
ii) Direct Mapping
iii) Set- associative Mapping
8. What is write – through in caches write?
If the main memory is updated with every memory write operation, with cache memory in parallel
9. What is write- back in cache write?
Only the cache location will be updated during write operation, and the main memory will be updated only when the word is removed from cache.
10. What is valid bit?
Valid bit is the bit used for each word in cache, to indicate whether it contain valid data or not
11. What are the disadvantages of each mapping technique?
i) Associative mapping – Expensive than RAM, as match logic is associated with each cell
ii) Direct mapping – Reduce hit ratio, if words with same index and different tag are referenced repeatedly
Two words with same index and different tag values cannot reside in cache at same time
iii) Set- associative mapping- The increase in set need more bits in words, and also more complex comparison logic
Other Questions………
1. Explain cache memory and the mapping technologies involved in it? (16)
2. Briefly explain about associative mapping (4)
3. Explain direct mapping (8)
4. Explain about set- associative mapping (6)
5. How data can be written into cache (6) ¶ 8:44 PM
Cache memory is the fastest in memory hierarchy, which contain the in formations and instructions which are most frequently reference and currently in execution
2. What is locality of reference?
The reference of memory at a given interval of time is confined within a few localized areas in memory. This phenomenon is the property of locality of reference
3. Define cache hit.
When CPU tries to access a word, and if the referenced word is found in cache, it is cache hit
4. Define Cache miss
If the CPU is not able to find a word in cache, and it check in main memory, it is called cache miss
5. Define hit ratio
The ratio of number of cache hits to the total number of references
6. Define miss ratio
The ratio of number of cache misses to the total number of references
7. Define mapping
The transformation of data from main memory to cache memory is mapping
There are 3 types of mapping
i) Associative Mapping
ii) Direct Mapping
iii) Set- associative Mapping
8. What is write – through in caches write?
If the main memory is updated with every memory write operation, with cache memory in parallel
9. What is write- back in cache write?
Only the cache location will be updated during write operation, and the main memory will be updated only when the word is removed from cache.
10. What is valid bit?
Valid bit is the bit used for each word in cache, to indicate whether it contain valid data or not
11. What are the disadvantages of each mapping technique?
i) Associative mapping – Expensive than RAM, as match logic is associated with each cell
ii) Direct mapping – Reduce hit ratio, if words with same index and different tag are referenced repeatedly
Two words with same index and different tag values cannot reside in cache at same time
iii) Set- associative mapping- The increase in set need more bits in words, and also more complex comparison logic
Other Questions………
1. Explain cache memory and the mapping technologies involved in it? (16)
2. Briefly explain about associative mapping (4)
3. Explain direct mapping (8)
4. Explain about set- associative mapping (6)
5. How data can be written into cache (6) ¶ 8:44 PM
