Questions tagged [cpu-pipelines]

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About the connection of pipelined execution and latency

Let's consider we want to calculate a[i]=a[i]*c for a vector the size of N=12 on some random processor. We do assume that ...
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Double Write After Write Dependency in out-of-order/in-order executions

What is going to happen when we have a WAW(write after write) dependency which consists of two consecutive WRITE instructions into the same register. We know we can solve a simple WAW dependency by ...
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How to compute the Cycles in a pipelined single cycle processor

I'm an undergrad studying computer engineering and I'm in my first of many courses on computer organization/architecture. In the lectures and online I see diagrams like the one pictured below from the ...
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Difficulty in understanding the concept of operand forward in pipeling and when to use split phase

Given below is a question from $\text{GATE } 2015 \text{ CS}$ paper, Consider the sequence of machine instruction given below: \begin{array}{ll} \text{MUL} & \text{R5, R0, R1} \\ \text{DIV} &...
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Calculating the pipeline speed up in case we have an infinite amount of stages

I have the following question: We begin with a computer implemented in single-cycle implementation. When the stages are split by functionality, the stages do not require exactly the same amount of ...
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Why cannot Operand forwarding remove all RAW hazards?

I read a statement in the textbook that : Operand Forwarding cannot remove all RAW Hazards in Pipelined Processor but am unable to conceptualize that in my brain. Can you please explain it with an ...
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2answers
761 views

How to improve the CPI and Speed up factor in CPU-OS simulator?

I am using the CPU-OS simulator by Besim Mustafa(https://www.merlot.org/merlot/viewMaterial.htm?id=476196) and I am studying Pipeline Stages. I have written a simple program and captured the metrics ...
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How can I get 8 bits output from 4 bit CPU?

I am very new to Computer architecture. I am thinking to add one more output register to this 4 bit CPU as shown below. However, I am not sure should I connect the output register to the current CPU. ...
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Detecting Data and Control Hazards for a mips 5 stage pipeline

I'm practicing data and control dependencies, but having trouble detecting them. For this example, I'm assuming this pipeline is fully bypassed (with forwarding). I think the only data dependency is ...
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1answer
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MIPS pipeline: choosing between slowing down a stage and adding a new stage

Suppose a new, more complicated, instruction is desired for this simple pipelined MIPS processor. Suppose, also, it could be implemented by either (a) adding new logic to the execute stage of the ...
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Neural branch predictors linear, classical predictors exponential, in resources?

Wikipedia states: The main advantage of the neural predictor is its ability to exploit long histories while requiring only linear resource growth. Classical predictors require exponential resource ...
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How many RAW dependencies are present in these instructions?

What is the number of RAW dependencies in below set of instructions? I1: R1 = R2 - R3 I2: R2 = R1 + R3 I3: R3 = R1 + R2 I4: R1 = R2 - R2 I can see the following ...
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Deep pipeline - cpu architecture

I was reading and learning about SIMD and AVX2 vector instruction, as I was trying to implement them for better performance. While reading about vector instruction, I encountered the term deep ...
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How to make single cycle processor pipelined?

I was asked that how can one make a single cycle processor pipelined on a CS course without any specifications regarding the design. I suppose, that I should answer that what should be changed on ...
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2answers
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How can instruction fetch and decode pipeline stages run simultaneously in a CPU with dynamic branch prediction?

I have recently been investigating CPU pipelining and branch prediction and have a question about how exactly these fit together. If, for example, instructions are meant to be fetched in one stage of ...
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Confusion in speed up calculation for pipeline architecture

This is an online question I am trying to solve. You are given a non-pipelined processor design which has a cycle time of 10ns and average CPI of 1.4.If a pipelined processor having 5 stages are 1ns, ...
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83 views

Calculate Stages in Non-Pipelined Processor

I have tried to attempt a question where I have to find the number of stages for non-pipelined processor(8085) for below program :- ...
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1answer
991 views

In instructions pipelining, why does register read/write take up only half clock cycle?

While studying instruction pipelining in MIPS processor, we make an assumption that registers read/write stages take only a half clock cycle, as this picture shows (half clock cycles are dotted in ...
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2answers
72 views

Why reverse pipeline stages in cycle-level simulator?

In pipeline simulator exercise, it says that: Traversing the stages in backwards order simplifies the instruction flow through the pipeline. Also, in gpgpu-sim source code, the stages are reversed ...
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Case where anti-dependency doesn't need pipeline stalling

While exploring the various types of data hazards in a pipeline, I came across a statement in my book which said that anti-dependency mayn't lead to cycle stalling. But i couldnt find at example for ...
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From where does the Fetch Unit get its instructions?

In the ARM Architecture pipelining stages, we know that the instructions pass from fetch to decode and so on? But, from where does the fetch unit get the instructions?
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Data Hazard in Pipelining

To be precise I am here for RAW hazard. Consider a 5 stage pipeline . In case of $I_4-I_1$ dependency , I am not sure if it is an $RAW$ hazard as $I_4$ does not depends on value of $R_1$ that $...
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Any CPUs using value prediction, dynamic instruction reuse?

There is a lot of research about techniques that try to reuse the previous result of an instruction, either memory loads or arithmetic, such as dynamic instruction reuse, value prediction, based on ...
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Branch Prediction question

My question relates to a video I watched on YouTube. The pipeline is a 5-stage pipeline which include fetch, decode, ALU, Mem (data), and Write. It mentions that nothing is fetched until we're sure ...
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392 views

Short pipeline or long pipeline

What is meant by a short pipeline? Does that mean the instructions are split into small number of pieces OR length of a piece is short?
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Load and Store Data hazard problem in 5-stages pipeline

Hi everyone and first of all thank you for been reading. I'm a little confused about data hazard dependences when a "Store" instruction is followed by a "Load" instruction. (Assume that we're working ...
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2answers
361 views

Difference between delayed branches and out-of-order execution

I have been reading about instruction pipeline and I stumbled upon the term delayed branches. From what I have understood, delayed branches will keep the pipeline busy, by executing instructions, ...
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1answer
308 views

How earliest that the data TLB (Translation Lookaside Buffer) can be accessed in an instruction execution pipeline?

In an instruction execution pipeline, the earliest that the data TLB (Translation Lookaside Buffer) can be accessed is: List item before effective address calculation has started during effective ...
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247 views

Pipeline question

I have this multiple choice question from a computer architecture class, a mips processor executes a program at 10 sec, without pipelining and clock rate 100 MHz. When running the program on a ...
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What are the prerequisites for instruction pipelining to work?

When can it be applied? When can it not be used? I get the general idea but not what it takes to make it work.
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How is the control unit affected by pipelining? [closed]

Compared to not using instruction pipelining. What is different?
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Pipelining without operand forwarding

I've been doing the HPC course from Udacity (https://classroom.udacity.com/courses/ud007/l) One of the problems is as follows (apologies for the image, as I was unable to format this using $\LaTeX$): ...
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1answer
106 views

CPU pipelining stages

I have read that in some pipelined architectures, memory access requires more than just one clock cycle. In that case how does processor handles the next instruction if the next instruction tries to ...
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1answer
2k views

Bubble in a pipeline

When NOPs are introduced in the pipeline by the control unit, how does they really cause the pipeline to stall? I mean, at every clock cycle, the pipeline register will eventually forward its contents ...
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1answer
364 views

The total time require for a pipeline to execute

The book says that a total time required for a pipeline with k stages to execute n instructions is as follows. $T _{k,n} =[pqnk+(1-pq)(k+n-1)] \tau$ p is the probability of encountering a branch ...
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131 views

predication execution, branch prediction

Below is a paragraph from a book. In an ordinary superscalar processor, we would use branch prediction to guess which of the given instructions is to be executed, and go down that path. If the ...
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1answer
522 views

Is finding cache size possible with information given?

An 8-way set-associative cache is used in a computer in which the real memory size is 222 bytes. The line size is 16 bytes, and there are 26 lines per set. A) What is the size of the cache in bytes? ...
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523 views

MIPS Pipeline Hazards - Branch Delay Slot

I'm confused about this exercise. We have assembly code: ...
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2answers
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Do unconditional branches cause control hazards?

Do unconditional branches, such as jump/goto instructions cause control hazards? If so, why? I am wondering because if ...
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How can I make a pipeline with undefined/unlimited stages?

I've been told that if you understand a pipeline then you should be able to make it with any depth, but I can only do 4 stages and maybe 5 if the memory is not too slow. How can I learn how to make ...
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543 views

Types of pipelining?

if pipelining is devided to polyfunctional pipelining and monofunctional pipelining(im sorry im not a native speaker the name may be incorect) and the polyfunctional pipelining is futher devided to ...
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Why do processor designers allow some pipeline hazards to occure [closed]

Actually this is a exam paper question I found during studying pipelined MIPS architecture.My idea is designers allow to occur hazards because of the cost to make complex design to prevent hazards,so ...
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2answers
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Whats the point of caching if the minimum single clock cycle time is the prorogation delay of the slowest component (fetching from DRAM)?

I know that the clock speed is determined by the slowest stage within the processor (usually fetch) because one clock cycle will take as much time as the slowest pipeline stage to ensure everything is ...
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What is the impact of locality principles on the pipelining techniques?

I know what are both locality principles and pipelining techniques. But I can't see any sort of interconnection between the two things. How can locality principles impact pipelining techniques?
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lw and sw hazards example MIPS

The below example confused me: lw $r0, 4($r0) sw $r0, 4($r0) add $r0, $r0, $r0 Using MIPS 5 stage execution what are the hazards we have 1) without forwarding 2) ...
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how long will it take to execute a ten-stage pipeline

Suppose you design a computer with a ten-stage Pipeline to execute one instruction, with each stage taking 5nsec A)how long ...
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how long will it take to execute a ten-stage pipeline [duplicate]

Suppose you design a computer with a ten-stage Pipeline to execute one instruction, with each stage taking 5nsec A)how long ...
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1answer
274 views

Execution time of a linear pipeline

A simple linear pipeline has three stages. The execution times in the stages are 10, 15, and 12 units respectively. If the pipeline is used to process 100 inputs, then the execution time is (a)...
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1answer
628 views

how one memory can be accessed simultaneously in instruction fetch and data read?

In modern computer architecture, pipeline has stage that access memory for normal data and instruction in parallel. But datas and instructions are usually in same memory, and their access address is ...
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Architecture, microarchitecture and ISA in microprocessor [duplicate]

What is Architecture, microarchitecture and ISA in processor. How do they relate to each other and what is the difference between them. Elucidate their differences with examples so that it is ...