L-3.6: Direct Mapping with Example in Hindi | Cache Mapping | Computer Organisation and Architecture

TL;DR

This video explains the concept of direct mapping in computer architecture, including block division, cache size, line number, block offset, address generation, and cache hit/miss.

Transcript

Hello friends, welcome to Gate Smashers In today's video we are going to discuss Direct Mapping As in last video we discussed about cache Mapping How many ways we can do mapping Either it is Direct, Fully Associative or K-way Set Associative So in this video we are going to talk about Direct Mapping And in this video I am going to discuss a... Read More

Key Insights

• 🫥 Direct mapping is a cache mapping technique that assigns each block of the main memory to a specific line in the cache based on the formula K mod N.
• 🚫 The main memory is divided into fixed-size blocks, with this example using 4 words per block, and the cache is divided into lines to accommodate the blocks.
• 🚫 CPU generates physical addresses to access specific words in the main memory, and the address is divided into block number and block offset.
• 🎁 Cache hit occurs when the requested block or word is already present in the cache, while cache miss occurs when it is not present, requiring replacement.

Questions & Answers

Q: What is direct mapping in computer architecture?

Direct mapping is a cache mapping technique that assigns each block of the main memory to a specific line in the cache. The mapping is determined using the formula K mod N, where K is the block number and N is the number of lines in the cache.

Q: How is the main memory divided into blocks and lines?

The main memory is divided into fixed-size blocks, with this example using 4 words per block. The cache is divided into lines, and the size of a line is equal to the size of a block in order to avoid internal fragmentation.

Q: How are addresses generated in the CPU and resolved?

CPU generates physical addresses for accessing specific words in the main memory. The address is divided into block number and block offset. The block number is used to determine the line number in the cache, while the block offset represents the position of the word within the block.

Q: What is a cache hit and cache miss in direct mapping?

A cache hit occurs when the block or word requested by the CPU is already present in the cache. A cache miss occurs when the requested block or word is not present in the cache, requiring the replacement of a cache line with the required block.

Key Insights:

• Direct mapping is a cache mapping technique that assigns each block of the main memory to a specific line in the cache based on the formula K mod N.
• The main memory is divided into fixed-size blocks, with this example using 4 words per block, and the cache is divided into lines to accommodate the blocks.
• CPU generates physical addresses to access specific words in the main memory, and the address is divided into block number and block offset.
• Cache hit occurs when the requested block or word is already present in the cache, while cache miss occurs when it is not present, requiring replacement.
• Understanding the architecture, block division, and address generation is crucial for efficiently accessing and managing memory in computer systems.

Summary & Key Takeaways

• Direct mapping is a cache mapping technique that involves dividing the main memory into fixed-size blocks and mapping them to specific lines in the cache.

• The size of the main memory is 128 words, with 4 words per block, resulting in a total of 32 blocks.

• CPU generates addresses for accessing specific words in the memory and can determine the corresponding line and block offset using the direct mapping formula.