Practice Question (Gate 2010)

Duration: 6 min

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Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. Paper 2 | Digital Logic: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep
  3. Paper 2 | Computer Organization And Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Control Unit Design, Instr Formats & Modes, Programming the Basic Computer
  4. Paper 2 | Analog And Digital Communication: Introduction to Communication Systems & Random Signals, Analog Communication Systems, Information Theory & Digital Communication Fundamentals, Digital Modulation & Detection Techniques, Error Control, Synchronization & Multiple Access Techniques
  5. Paper 2 | Programming in C: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  6. Paper 2 | Data Structures And Programming: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Java, OOPS with C++, Java Fundamentals, Array, String, IO & References
  7. Paper 2 | Algorithms: Algorithm Analysis, Sorting Algorithms, Time Complexity Analysis, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  8. Paper 2 | Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  9. Paper 2 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS, Linux OS
  10. Paper 2 | Databases: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Relational Calculus, File Organization & Indexing, Transaction Management, Concurrency Control
  11. Paper 2 | Information Systems and Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  12. Paper 2 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware Basics
  13. Paper 2 | Internet & Web Technologies: Website, Browser & Services, Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, HTML Basics, JavaScript-Basics, CSS, XML, HTML5
  14. Paper 2 | Cyber Security And Emerging Technologies: Emerging Tech Trends
  15. Paper 2 | Cloud Technology: Cloud Computing
  16. Paper 2 | Probability and statistics: Probability, Statistics
  17. Paper-1 English: Vocabulary, Preposition, Articles, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Cloze Test (Cloze Passage), Sentence Construction
  18. Paper 1 General Mental Ability & Logical reasoning: Ratio and Proportion (Ratios), Divisibility Rules, Data Interpretation, Mixture and Alligation, Permutation and Combination, Logarithm, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Percentage, Average, Powers and Exponents (Surds and Indices), Algebra, Profit and Loss, Simple Interest and Compound Interest, Time and Work, Pipe and Cistern, Mensuration and Geometry, Mental Ability, Age Problems, Partnership, Arithmetic, Speed Mathematics and Basic Mathematics, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Seating Arrangements, Blood Relations, Directions (Direction Test), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Selection Decision Table (Decision Making), Logical Sequence Of Words, Venn Diagram, Analogy
  19. Paper-1 General Knowledge & Current Affairs: State Wise GK, History, Geography, GK- Current Affairs, Static General Knowledge
  20. Full Length Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video analyzes a GATE 2010 computer architecture problem involving a 5-stage pipelined processor. The core task is to calculate the total clock cycles required for a sequence of four instructions: MUL, DIV, ADD, and SUB. The processor architecture features five stages: Instruction Fetch (IF), Instruction Decode (ID), Operand Fetch (OF), Perform Operation (PO), and Write Back (WO). The IF, ID, OF, and WO stages each consume one clock cycle. However, the PO stage duration varies based on instruction type: 1 cycle for ADD and SUB, 3 cycles for MUL, and 6 cycles for DIV. The problem explicitly states that operand forwarding is utilized to mitigate data hazards, allowing dependent instructions to access results as soon as they are produced in the PO stage rather than waiting for the WO stage. The video demonstrates how to construct a pipeline timing diagram to visualize instruction execution and identify stalls caused by data dependencies, specifically read-after-write hazards where an instruction requires a result from a preceding instruction that has not yet completed its PO stage.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens by presenting the GATE 2010 problem statement on screen, displaying a 5-stage pipelined processor configuration. The text explicitly lists the instruction latencies: IF, ID, OF, and WO take 1 cycle each. The PO stage duration is variable: 1 cycle for ADD/SUB, 3 cycles for MUL, and 6 cycles for DIV. The instructor introduces the instruction sequence I0 through I3: MUL R2, R0, R1; DIV R5, R3, R4; ADD R2, R5, R2; SUB R5, R2, R6. The problem asks for the total clock cycles needed to execute this sequence given that operand forwarding is used. An empty grid appears on screen, intended for mapping the pipeline execution cycle by cycle.

  2. 2:00 – 5:00 02:00-05:00

    The instructor begins constructing the pipeline timing diagram to solve the problem. He maps the first instruction, MUL R2, R0, R1 (I0), into the pipeline stages. I0 enters IF at cycle 1 and proceeds through ID, OF, and PO. Since MUL requires 3 cycles in the PO stage, it occupies cycles 4, 5, and 6. The instructor highlights that the result of I0 becomes available at the end of cycle 6 due to operand forwarding. Next, he places DIV R5, R3, R4 (I1) into the pipeline. I1 starts at cycle 2 and proceeds through IF, ID, OF. It encounters a dependency check but since it does not depend on I0's result immediately in the OF stage, it proceeds to PO. The DIV instruction requires 6 cycles in PO, occupying cycles 7 through 12. The instructor marks the timeline to show that I1's result is available at the end of cycle 12.

  3. 5:00 – 5:55 05:00-05:55

    The final segment focuses on resolving data hazards for the remaining instructions, ADD and SUB. The instructor analyzes I2: ADD R2, R5, R2. This instruction depends on the result of I0 (R2) and I1 (R5). Since operand forwarding is used, the instructor checks if results are available. R2 from I0 is ready after cycle 6, and R5 from I1 is ready after cycle 12. The ADD instruction enters the OF stage and must wait for R5, causing a stall or delay until cycle 13. The instructor calculates the total cycles by extending the timeline to ensure all instructions complete their WO stage. The final calculation suggests a total of 17 clock cycles, matching option (C) in the multiple-choice question displayed on screen. The video concludes with the completed pipeline diagram showing stalls and varying PO durations.

The video effectively demonstrates the application of pipeline timing diagrams to solve complex computer architecture problems involving variable instruction latencies and data hazards. The key takeaway is the critical role of operand forwarding in reducing stalls, as it allows dependent instructions to proceed without waiting for the Write Back stage. The variable duration of the PO stage is a crucial factor that complicates the timing, requiring careful tracking of when each instruction's result becomes available. The problem-solving approach involves mapping each instruction to the pipeline stages, identifying dependencies between registers (R2 and R5), and calculating stalls based on when the required operands are produced. The final answer of 17 cycles is derived by ensuring all four instructions complete their WO stage, accounting for the extended PO durations of MUL and DIV. This method is essential for students preparing for exams like GATE, where understanding pipeline hazards and forwarding mechanisms is fundamental.

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