Why do we need so many different addressing modes? Explain the concept behind instruction pipelining. What is the theoretical speedup for a 4-stage pipeline with a 20ns clock cycle if it is processing...

Why do we need so many different addressing modes? Explain the concept behind instruction pipelining. What is the theoretical speedup for a 4-stage pipeline with a 20ns clock cycle if it is processing 100 tasks? What are the pipeline conflicts that can cause a slowdown in the pipeline?