Practice Question (Gate 2010)

Duration: 6 min

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Module outline

  1. About Course: About the Course
  2. CS | 01 | Digital Logic and Circuits and Discrete Mathematical Structures: Digital Systems & Boolean Basics, Number System, Number Representation, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Permutation and Combination
  3. CS | 02 | Computer Organization and Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Multiprocessors
  4. CS | 03 | Data Structures and Algorithm: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Complexity Theory, Advanced Algorithms
  5. CS | 04 | Problem Solving through C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  6. CS | 05 | Object Oriented Techniques: Object Oriented Technology, Java
  7. CS | 06 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Unix OS
  8. CS | 07 | Database Management Systems: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, Database Security & Authorization, Query Processing & Optimization, File Organization & Indexing
  9. CS | 08 | 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
  10. CS | 09 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  11. CS | 10 | Internet Technology, Web Design and Web Technology: Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, JavaScript-Basics, HTML Basics
  12. CS | 11 | System Analysis And Design: Fundamentals of Systems and Information Systems, SDLC and Development Approaches, Software Documentation and Software Requirements Specification (SRS), SDD and Quality Assurance, Security, Risk Management & Maintenance
  13. CS | 12 | Information Security and Cyber Laws: Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Electronic Data Interchange and E-Commerce, Physical Security and Cryptography Basics, Intrusion Detection Systems (IDS), Cyber Safety and Security
  14. CS | 13 | Computer Graphics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing
  15. GS Paper | 01 | Indian and World Geography: Geography
  16. GS Paper | 02 | History: History
  17. GS Paper | 03 | Indian Economy & Social Development: Indian Economy
  18. GS Paper | 04 | General Science: Biology, Chemistry, वैज्ञानिक उपलब्धियाँ और अनुसंधान / Scientific Achievements and Research
  19. GS Paper | 05 | Elementary Maths: संख्या पद्धति / Number System, Divisibility Rules, महत्तम समापवर्तक और लघुत्तम समापवर्त्य / HCF and LCM, प्रतिशत / Percentage, लाभ, हानि और बट्टा / Profit, Loss and Discount, साधारण और चक्रवृद्धि ब्याज / Simple and Compound Interest, अनुपात और समानुपात / Ratio and Proportion, औसत / Average, समय और कार्य / Time and Work, समय, चाल और दूरी / Time, Speed and Distance, Algebra, घन क्षेत्रमिति / Solid Mensuration, आँकड़ा निर्वचन / Data Interpretation, Arithmetic, Statistics, Probability, Sequence and Series (Series), मिश्रण और एलिगेशन / Mixture and Alligation, Calculus, Trigonometry, Vectors, संख्या पद्धति और संख्या सिद्धांत / Number Systems and Number Theory, यूक्लिडीय ज्यामिति और क्षेत्रमिति / Euclidean Geometry and Mensuration, सांख्यिकी और प्रायिकता / Statistics and Probability, निर्देशांक ज्यामिति, सदिश और त्रिविमीय ज्यामिति / Coordinate Geometry, Vectors and 3D Geometry, बहुपद, समीकरण और सम्मिश्र संख्याएँ / Polynomials, Equations and Complex Numbers, समतल क्षेत्रमिति / Plane Mensuration, सरलीकरण, घातांक और करणी / Simplification, Indices and Surds, समुच्चय, संबंध, फलन और विविक्त गणित / Sets, Relations, Functions and Discrete Mathematics
  20. GS Paper | 06 | Indian Polity and Governance: Polity
  21. GS Paper | 07 | Current Events: समसामयिकी / Current Affairs
  22. UPLT Live Classes Notes: UPLT Live Classes
  23. UPLT Full Mock Tests Tier 1:
  24. UPLT Full Mock Tests Tier 2:
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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