Data Hazards

Duration: 4 min

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Module outline

  1. About Course: About the Course
  2. Paper-2 | Programming & Data Structures: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  3. Paper-2 | Databases / DBMS & SQL: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control
  4. Paper-2 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  5. Paper-2 | Computer Networks & Security: 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, Network Access Technologies, Network Security
  6. 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
  7. 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
  8. Paper-2 | Theory of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines
  9. Paper-2 | Computer Organization & Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
  10. 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
  11. Paper-1 | General Awareness: Polity, Physics, Biology, Chemistry, Static General Knowledge, GK- Current Affairs, History, Geography, Indian Economy, Environment
  12. Paper-1 | Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Data Interpretation, Blood Relations, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Clock, Calendar, Cubes & Dices, Directions (Direction Test), Analogy, Seating Arrangements, Analytical Reasoning (Counting Figures Reasoning)
  13. Paper-1 | Quantitative Aptitude: Ratio and Proportion (Ratios), Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Speed Time and Distance, Average, Age Problems, Percentage, Profit and Loss, Time and Work, Pipe and Cistern, Simple Interest and Compound Interest, Powers and Exponents (Surds and Indices), Mensuration and Geometry, Probability, Statistics, Arithmetic, Algebra
  14. Paper-1 | English: Vocabulary, 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), Sentence Construction, Cloze Test (Cloze Passage)
  15. Coal India Previous Year Paper:
  16. Engineering Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Linear Algebra, Calculus
  17. Coal India Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video lecture provides a comprehensive overview of Data Hazards in computer architecture, specifically within the context of pipelined processors. The instructor begins by defining data hazards as situations where instructions exhibiting data dependence modify data in different pipeline stages, which causes delays in the pipeline execution. He introduces the Bernstein condition as the underlying principle for these dependencies. The lecture categorizes hazards into three main types: RAW (Read after Write), WAR (Write after Read), and WAW (Write after Write). The session progresses from general definitions to specific, concrete examples, illustrating how these dependencies manifest in instruction sequences and cause performance issues.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the concept of Data Hazards using a slide titled Data Hazards. He explains that these occur when instructions with data dependence modify data in different pipeline stages, leading to delays. He lists three types: RAW (Flow/True data dependency), WAR (Anti-Data dependency), and WAW (Output data dependency). He then starts writing an example on the whiteboard to illustrate a dependency. He writes I1: a = b + c and I2: d = a + c. He circles the variable a in both instructions, drawing an arrow from the write operation in I1 to the read operation in I2. This visual aid demonstrates a Read-After-Write dependency where the second instruction needs the result of the first. He emphasizes that I2 is trying to read a before I1 has written it in the pipeline context.

  2. 2:00 – 4:18 02:00-04:18

    The slide updates to provide formal definitions and examples for each hazard type. First, RAW hazard is defined: instruction J tries to read data before instruction, I write it. The example given is I: R2 <- R1 + R3 followed by J: R4 <- R2 + R3, where R2 is written by I and read by J. Next, WAR hazard is defined: instruction J tries to write data before instruction, I read it. The example is I: R2 <- R1 + R3 and J: R3 <- R4 + R5, highlighting the conflict on register R3. Finally, WAW hazard is defined: instruction J tries to write output before instruction, I write it. The example shows I: R2 <- R1 + R3 and J: R2 <- R4 + R5, both writing to R2. The instructor concludes by noting that WAR and WAW hazards typically occur during out-of-order execution. He uses red circles and arrows to visually track the read and write operations on specific registers.

The lecture systematically breaks down data hazards, starting with a high-level definition and the Bernstein condition. It then details the three specific types: RAW, WAR, and WAW. The instructor uses both handwritten examples and slide-based formal definitions to reinforce the concepts. The progression moves from a simple variable assignment example (a = b + c) to register transfer notation (R2 <- R1 + R3), making the abstract concept of pipeline hazards concrete. The distinction between hazards that occur in standard execution (RAW) versus those requiring out-of-order execution (WAR, WAW) is a key takeaway. The visual annotations, such as circling registers and drawing arrows, serve as crucial aids for understanding the flow of data and the specific points of conflict in the pipeline.

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