Problem 1

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Texas A&M University, Corpus Christi *

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2437

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Industrial Engineering

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Oct 30, 2023

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docx

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Uploaded by AgentNeutronPolarBear19

Problem 1: Answer the following questions briefly (20 pts). a) What kinds of data hazards can be addressed by the register renaming? Please briefly describe how to use the register renaming to address those data hazards. Answer: In computer architecture, register renaming is a technique that abstracts logical registers from physical registers. Every logical register has a set of physical registers associated with it. There are three kind of hazards: Read-after-write (RAW): If a read is happening before the write that is in the previous instructions that is called RAW Write-after-write (WAW): If a write is happening before the write operation that is in the previous instruction that is called WAW Write-after-read (WAR): If a write is happening before the read from the previous instruction that is WAR. Instead of stalling the second instruction we can have two memory locations with old and new value. And update accordingly to in the memory b) What are the advantages of Reservation Stations over Hardware Registers for register renaming? Answer: Reservation Stations have better latency from rename to execute, because the rename stage finds the register values directly, rather than finding the physical register number, and then using that to find the value. This latency shows up as a component of the branch misprediction latency c) How does Tomasulo's algorithm speed up the performance while maintaining the illusion of sequentially for instructional parallelism? Answer: Tomasulo’s algorithm uses ROB and new commit to maintain performance while maintaining the illusion of sequentiality d) What are the lists of the importance of Common Data Bus to Tomasulo's algorithm? Answer: The main use of Common Data Bus(CDB) is to connect reservation stations and functional units. This can lead to two main advantages: 1) The functional units can access the data as soon as they are ready, instead of waiting for the access to register files 2) Hazard detection and control execution is distributed. Reservation stations control the execution instead of a single hazard unit

e) What are the advantages of Correlating Predictor over Local Predictor? Answer: Using a 2-bit prediction will give us max of 50% prediction rate due to the interference from other branches. Correlation Predictor performs better due to it takes the behavior of the other branches into consideration. Local predictor takes only the behavior of that specific branch into consideration. Leaving the rest of the branches. Advantages of Correlating Predictor over Local Predictor are: 1. Dynamic branch prediction 2. Random branch prediction 3. Next Line branch prediction 4. Saturating counter 5. Two- level adaptive predictor 6. Local branch prediction 7. Global branch prediction 8. Alloyed branch prediction

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