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An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,
a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.
b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.
a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.
b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.
Correct answer is 'Each stage is 2 ns.'. Can you explain this answer?
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Verified Answer
An instruction pipeline has five stages where each stage take 2 nanose...
Each stage is 2ns. So, after 5 time units each of 2ns, the first instruction finishes (i.e., after 10ns), in every 2ns after that a new instruction gets finished. This is assuming no branch instructions. Now, once the pipeline is full, we can assume that the initial fill time doesn't matter our calculations and average execution time for each instruction is 2ns assuming no
branch instructions.
(a) Now, we are given that 20% of instructions are branch (like JMP) and when a branch instruction is executed, no further instruction enters the pipeline. So, we can assume every 5th instruction is a branch instruction. So, with this assumption, total time to finish 5 instruction will be 5 * 2 + 8 = 18 ns (as when a branch instruction enters the pipeline and before it finishes, 4 pipeline stages will be empty totaling 4 * 2 = 8 ns, as it is mentioned in question that the next instruction fetch starts only when branch instruction completes). And this is the same for every set of 5 instructions, and hence the average instruction execution time = 18/5 = 3.6 ns
(b) This is just a complex statement. But what we need is to identify the % of branch instructions which cause a branch to be taken as others will have no effect on the pipeline flow.
20% of branch instructions are branch instructions. 80% of branch instructions are conditional.
That means .2*.8 = 16% of instructions are conditional branch instructions and it is given that 50% of those result in a branch being taken.
So, 8% of instructions are conditional branches being taken and we also have 20% of 20% = 4% of unconditional branch
instructions which are always taken.
So, percentage of instructions where a branch is taken is 8+4 = 12% instead of 20% in (a) part.
So, in 100 instructions there will be 12 branch instructions. We can do a different calculation here as compared to (a) as 12 is not a divisor of 100. Each branch instruction causes a pipeline delay of 4*2 = 8 ns. So, 12 instructions will cause a
delay of 12 * 8 = 96 ns. For 100 instructions, we need 100 * 2 = 200 ns without any delay and with delay we require 200 + 96 = 296 ns for 100 instructions.
So, average instruction execution time = 296/100 = 2.96 ns (We can also use this method for part (a) which will give 100 * 2 + 20*8 = 360 ns for 100 instructions)
branch instructions.
(a) Now, we are given that 20% of instructions are branch (like JMP) and when a branch instruction is executed, no further instruction enters the pipeline. So, we can assume every 5th instruction is a branch instruction. So, with this assumption, total time to finish 5 instruction will be 5 * 2 + 8 = 18 ns (as when a branch instruction enters the pipeline and before it finishes, 4 pipeline stages will be empty totaling 4 * 2 = 8 ns, as it is mentioned in question that the next instruction fetch starts only when branch instruction completes). And this is the same for every set of 5 instructions, and hence the average instruction execution time = 18/5 = 3.6 ns
(b) This is just a complex statement. But what we need is to identify the % of branch instructions which cause a branch to be taken as others will have no effect on the pipeline flow.
20% of branch instructions are branch instructions. 80% of branch instructions are conditional.
That means .2*.8 = 16% of instructions are conditional branch instructions and it is given that 50% of those result in a branch being taken.
So, 8% of instructions are conditional branches being taken and we also have 20% of 20% = 4% of unconditional branch
instructions which are always taken.
So, percentage of instructions where a branch is taken is 8+4 = 12% instead of 20% in (a) part.
So, in 100 instructions there will be 12 branch instructions. We can do a different calculation here as compared to (a) as 12 is not a divisor of 100. Each branch instruction causes a pipeline delay of 4*2 = 8 ns. So, 12 instructions will cause a
delay of 12 * 8 = 96 ns. For 100 instructions, we need 100 * 2 = 200 ns without any delay and with delay we require 200 + 96 = 296 ns for 100 instructions.
So, average instruction execution time = 296/100 = 2.96 ns (We can also use this method for part (a) which will give 100 * 2 + 20*8 = 360 ns for 100 instructions)
Most Upvoted Answer
An instruction pipeline has five stages where each stage take 2 nanose...
Calculation of Average Instruction Execution Time
Given:
- 5 stages in the instruction pipeline
- Each stage takes 2 nanoseconds
- All instructions use all five stages
- 20% of all instructions executed are branch instructions
- Branch instructions are not overlapped
To calculate the average instruction execution time, we need to consider the time taken by each instruction in the pipeline. Since each stage takes 2 nanoseconds, an instruction in the pipeline takes 10 nanoseconds (5 stages x 2 nanoseconds per stage) to execute.
For non-branch instructions, all five stages are used, so they take 10 nanoseconds to execute. However, for branch instructions, the instruction after the branch is not fetched till the branch instruction is completed. Therefore, branch instructions take longer to execute.
Let's assume that the branch instruction takes an additional 2 nanoseconds to complete. This is because once a branch instruction is encountered, the pipeline needs to be flushed and the new instructions need to be fetched from the new branch target address. Therefore, a branch instruction takes a total of 12 nanoseconds to complete.
Now, using the given information that 20% of all instructions executed are branch instructions, we can calculate the average instruction execution time as follows:
Average Instruction Execution Time = (0.2 x 12 nanoseconds) + (0.8 x 10 nanoseconds)
= 2.4 nanoseconds + 8 nanoseconds
= 10.4 nanoseconds
Therefore, the average instruction execution time is 10.4 nanoseconds.
Calculation of Average Instruction Execution Time for Conditional Branch Instructions
Given:
- 5 stages in the instruction pipeline
- Each stage takes 2 nanoseconds
- All instructions use all five stages
- 80% of all branch instructions are conditional branch instructions
- 50% of the conditional branch instructions are such that the branch is taken
In this case, we are considering the scenario where conditional branch instructions are executed. If the branch is taken, the following instructions can be overlapped. Therefore, the execution time of the conditional branch instructions will be shorter compared to the non-conditional branch instructions.
Let's assume that a conditional branch instruction takes an additional 1 nanosecond to complete. This is because if the branch is taken, the pipeline can continue with the next instruction without any delay. However, if the branch is not taken, there will be a delay of one stage (2 nanoseconds) before the next instruction can be executed. Therefore, a conditional branch instruction takes a total of 11 nanoseconds to complete if the branch is not taken, and 10 nanoseconds if the branch is taken.
Now, using the given information that 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, we can calculate the average instruction execution time as follows:
Average Instruction Execution Time = (0.2 x 12 nanoseconds) + (0.64 x 10 nanoseconds) + (0.16 x 11 nanoseconds)
= 2.4 nanoseconds + 6.4 nanoseconds + 1.76 nanoseconds
= 10.56 nanoseconds
Therefore, the average instruction execution time for conditional branch instructions is 10.56 nanoseconds.
Given:
- 5 stages in the instruction pipeline
- Each stage takes 2 nanoseconds
- All instructions use all five stages
- 20% of all instructions executed are branch instructions
- Branch instructions are not overlapped
To calculate the average instruction execution time, we need to consider the time taken by each instruction in the pipeline. Since each stage takes 2 nanoseconds, an instruction in the pipeline takes 10 nanoseconds (5 stages x 2 nanoseconds per stage) to execute.
For non-branch instructions, all five stages are used, so they take 10 nanoseconds to execute. However, for branch instructions, the instruction after the branch is not fetched till the branch instruction is completed. Therefore, branch instructions take longer to execute.
Let's assume that the branch instruction takes an additional 2 nanoseconds to complete. This is because once a branch instruction is encountered, the pipeline needs to be flushed and the new instructions need to be fetched from the new branch target address. Therefore, a branch instruction takes a total of 12 nanoseconds to complete.
Now, using the given information that 20% of all instructions executed are branch instructions, we can calculate the average instruction execution time as follows:
Average Instruction Execution Time = (0.2 x 12 nanoseconds) + (0.8 x 10 nanoseconds)
= 2.4 nanoseconds + 8 nanoseconds
= 10.4 nanoseconds
Therefore, the average instruction execution time is 10.4 nanoseconds.
Calculation of Average Instruction Execution Time for Conditional Branch Instructions
Given:
- 5 stages in the instruction pipeline
- Each stage takes 2 nanoseconds
- All instructions use all five stages
- 80% of all branch instructions are conditional branch instructions
- 50% of the conditional branch instructions are such that the branch is taken
In this case, we are considering the scenario where conditional branch instructions are executed. If the branch is taken, the following instructions can be overlapped. Therefore, the execution time of the conditional branch instructions will be shorter compared to the non-conditional branch instructions.
Let's assume that a conditional branch instruction takes an additional 1 nanosecond to complete. This is because if the branch is taken, the pipeline can continue with the next instruction without any delay. However, if the branch is not taken, there will be a delay of one stage (2 nanoseconds) before the next instruction can be executed. Therefore, a conditional branch instruction takes a total of 11 nanoseconds to complete if the branch is not taken, and 10 nanoseconds if the branch is taken.
Now, using the given information that 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, we can calculate the average instruction execution time as follows:
Average Instruction Execution Time = (0.2 x 12 nanoseconds) + (0.64 x 10 nanoseconds) + (0.16 x 11 nanoseconds)
= 2.4 nanoseconds + 6.4 nanoseconds + 1.76 nanoseconds
= 10.56 nanoseconds
Therefore, the average instruction execution time for conditional branch instructions is 10.56 nanoseconds.
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An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer?
Question Description
An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer?.
An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? for Computer Science Engineering (CSE) 2024 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer?.
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An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer?, a detailed solution for An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? has been provided alongside types of An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice An instruction pipeline has five stages where each stage take 2 nanoseconds and all instruction use all five stages. Branch instructions are not overlapped. i.e., the instruction after the branch is not fetched till the branch instruction is completed. Under ideal conditions,a. Calculate the average instruction execution time assuming that 20% of all instructions executed are branch instruction. Ignore the fact that some branch instructions may be conditional.b. If a branch instruction is a conditional branch instruction, the branch need not be taken. If the branch is not taken, the following instructions can be overlapped. When 80% of all branch instructions are conditional branch instructions, and 50% of the conditional branch instructions are such that the branch is taken, calculate the average instruction execution time.Correct answer is 'Each stage is 2 ns.'. Can you explain this answer? tests, examples and also practice Computer Science Engineering (CSE) tests.
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