1. What happens when the processor needs data and the block is not found in the

Question

1. What happens when the processor needs data and the block is not found in the cache and what term is used to identify this situation

2.

Consider a simple 64-byte direct-mapped cache with 8 byte blocks. Assume addresses are 16bits. The cache is physically tagged. The processor has 16KB of physical memory.

Describe the relationship between the physical memory, the cache, and addresses used by the processor

3.

What happens when the processor changes a block of data that is in the cache and what is the main issue?

4.

Briefly explain the disadvantage of polling for I/O status, identify an alternative, and briefly explain why it is better.

Explanation / Answer

The term which is used to Identify the situation is "PAGGING ERROR" When the processor changes the data that is in Cache memory there will be basically inconsistency problem.This is because when a cache is loaded it does not have contact with the memory until any other data is required other the data in the cache. When the processor copies the required data from memory into the cache then it does not again update until any change occurs in it or if any write back instruction is executed. Here, when other processes try to access the data, they read the data from memory which is an old data. So, when the cache is not updated to actual data in memory, inconsistency in will occur. This might be a very big problem when it comes to Distributed systems where the systems are scattered and inconsistency is an important factor.

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