Associative mapping in computer architecture

Associative Mapping – In this type of mapping, the associative memory is used to store content and addresses of the memory word. Any block can go into any line of the cache. This means that the word id bits are used to identify which word in the block is needed, but the tag becomes all of the remaining bits.

1. What is the difference between direct mapping and associative mapping?
2. What are the advantages of associative mapping?
3. What is fully associative mapping?
4. Why is associative mapping so expensive?
5. What is the advantage of fully associative cache?
6. What is set associative cache?
7. What is the disadvantage of fully associative cache?
8. Is TLB fully associative?
9. What is the advantage of associative mapping over direct mapping?
10. How does fully associative cache work?
11. What are the three fields in a set associative cache address and how are they used to access a location in cache?
12. How do you find the associative set of cache?
13. What is difference between unified and split cache?
14. Which memory has very high storage performance?

What is the difference between direct mapping and associative mapping?

What are the differences among direct mapping , associative mapping , and set- associative mapping ? - Direct mapping maps each block of main memory into only one possible cache line. - Associative mapping permits each main memory block to be loaded into any line of the cache.

What are the advantages of associative mapping?

In associative mapping both the address and data of the memory word are stored. The associative mapping method used by cache memory is very flexible one as well as very fast. This mapping method is also known as fully associative cache. Associative mapping is fast.

What is fully associative mapping?

Fully Associative Mapping is a cache mapping technique that allows to map a block of main memory to any freely available cache line.

Why is associative mapping so expensive?

If a hit occurs in one of the ways, a multiplexer selects data from that way. ... However, set associative caches are usually slower and somewhat more expensive to build because of the output multiplexer and additional comparators.

What is the advantage of fully associative cache?

Advantages. Fully associative cache structure provides us the flexibility of placing memory block in any of the cache lines and hence full utilization of the cache. The placement policy provides better cache hit rate.

What is set associative cache?

Set Associative Cache

• Set associative caches are a. compromise between fully associative caches and direct-mapped caches. In a set associative cache, there are a fixed number of locations (called a set) that a given address may be stored in. The number of locations in each set is the associative of the cache.

What is the disadvantage of fully associative cache?

Explanation: The major disadvantage of the fully associative cache is the amount of hardware needed for the comparison increases in proportion to the cache size and hence, limits the fully associative cache.

Is TLB fully associative?

The TLB is typically constructed as a fully or highly associative cache, where the virtual address is compared against all cache entries. If the TLB hits, the contents of the TLB are used for the translation, access permissions, and so on. The management of the TLB is shared between the operating system and hardware.

What is the advantage of associative mapping over direct mapping?

Full associative mapping has much less potential for collisions between blocks trying to occupy the cache. That is, two or more main memory blocks may have to fit into the same cache block with direct mapping, but could go into different cache blocks with a full (or set) associative mapping.

How does fully associative cache work?

A fully associative cache permits data to be stored in any cache block, instead of forcing each memory address into one particular block. — When data is fetched from memory, it can be placed in any unused block of the cache.

What are the three fields in a set associative cache address and how are they used to access a location in cache?

In set associative cache mapping, a memory reference is divided into three fields: tag, set, and word, as shown below. As with direct-mapped cache, the word field chooses the word within the cache block, and the tag field uniquely identifies the memory address.

How do you find the associative set of cache?

To determine the number of bits in the SET field, we need to determine the number of sets. Each set contains 2 cache blocks (2-way associative) so a set contains 32 bytes. There are 32KB bytes in the entire cache, so there are 32KB/32B = 1K sets. Thus the set field contains 10 bits (2¹⁰ = 1K).

What is difference between unified and split cache?

Disadvantages of the Split Cache Design

A cache line that contains both instructions and data may exist in both caches at the same time. In contrast, in a unified cache, only a single copy of the line would exist in the cache.

Which memory has very high storage performance?

Cache memory operates between 10 to 100 times faster than RAM, requiring only a few nanoseconds to respond to a CPU request. The name of the actual hardware that is used for cache memory is high-speed static random access memory (SRAM).