Podcast
Questions and Answers
What are the four key current directions in computer architecture?
What are the four key current directions in computer architecture?
The ____ is the interface between hardware and the lowest level software.
The ____ is the interface between hardware and the lowest level software.
ISA
What is the role of the compiler in the software development process?
What is the role of the compiler in the software development process?
The compiler translates high-level language code (such as C, C++, or Java) into assembly code, which is a lower-level language closer to the machine's instruction set.
Which components make up the five classic components of a computer?
Which components make up the five classic components of a computer?
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What is the difference between computer architecture and computer organization?
What is the difference between computer architecture and computer organization?
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The PostPC Era marked the shift from personal computers to mobile devices and cloud computing.
The PostPC Era marked the shift from personal computers to mobile devices and cloud computing.
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What are the eight great ideas in computer architecture?
What are the eight great ideas in computer architecture?
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What are the two main measures of computer performance?
What are the two main measures of computer performance?
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To maximize performance, we want to minimize response time or execution time for a given task.
To maximize performance, we want to minimize response time or execution time for a given task.
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What are the two types of execution time used to measure computer performance?
What are the two types of execution time used to measure computer performance?
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How does CPU clocking relate to the operation of digital hardware?
How does CPU clocking relate to the operation of digital hardware?
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What is the relationship between CPU Time, Clock Cycles, and Clock Cycle Time?
What is the relationship between CPU Time, Clock Cycles, and Clock Cycle Time?
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Which of the following factors can improve the performance of a computer system?
Which of the following factors can improve the performance of a computer system?
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What is CPI, and why is it a weighted average?
What is CPI, and why is it a weighted average?
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Study Notes
Course Information
- Course Title: Computer Architecture
- Course Code: CS 320
- Instructor: Dr. Khaled El Helow
- Email: [email protected]
Lecture 1: Introduction and Basics
- Four Key Current Directions:
- Fundamentally Secure/Reliable/Safe Architectures
- Fundamentally Energy-Efficient Architectures
- Memory-Centric (Data-Centric) Architectures
- Fundamentally Low-Latency and Predictable Architectures
- Architectures for AI/ML, Genomics, Medicine, Health
The Transformation Hierarchy
- The hierarchy of components, from highest level to lowest level:
- Problem
- Algorithm
- Program/Language
- System Software
- SW/HW Interface
- Micro-architecture
- Logic
- Devices
- Electrons
Classes of Computers
- Personal Computers:
- General-purpose
- Variety of software
- Subject to cost/performance tradeoffs
- Server Computers:
- Network-based
- High capacity, performance, reliability
- Range from small servers to building-sized
- Supercomputers:
- High-end scientific and engineering calculations
- Highest capability but a small fraction of the computer market
- Embedded Computers:
- Hidden as components of systems
- Stringent power/performance/cost constraints
Units of Measurement
- Decimal and binary units and their abbreviations, along with the percentage increase between decimal and binary values
The PostPC Era
- Personal Mobile Device (PMD):
- Battery-operated
- Connects to the Internet
- Relatively inexpensive
- Examples: smartphones, tablets, electronic glasses
- Cloud Computing:
- Warehouse Scale Computers (WSC)
- Software as a Service (SaaS)
- Portion of software runs on a PMD and in the cloud
- Examples: Amazon, Google
Eight Great Ideas
- Design for Moore's Law
- Use abstraction to simplify design
- Make the common case fast
- Performance via parallelism
- Performance via pipelining
- Performance via prediction
- Hierarchy of memories
- Dependability via redundancy
Abstraction Layers in Computing
- A layered structure that hides the complexity of details at each level to simplify programming. Application programs don't need to interact with basic physics.
- A large gap exists between the application level and the physical layer, requiring multiple intermediary steps.
Abstraction Layers in Computing Details
- Application: Algorithms, Programming Languages, Compiler, Linker, Run-time Libraries
- Operating System, Virtual Machines
- Instruction Set Architecture (ISA)
- Microarchitecture
- Logic Gates, Circuits
- Devices, Layout
- Physics
Hardware and Software Components and Performance
- Algorithm: Determines the number of source-level statements and I/O operations executed.
- Programming language, compiler, and architecture: Determine the number of computer instructions for source-level statements.
- Processor and memory system: Determines how quickly instructions can be executed.
- I/O system (hardware and operating system): Determines how quickly I/O operations can be executed.
Computer Architecture
- Defined as the combination of instruction set architecture and computer organization.
Computer Architecture vs Computer Organization
- Computer Architecture describes what the computer does. It deals with high-level design issues. It essentially specifies the hardware interfaces to the software.
- Computer Organization describes how the computer does it. It deals with low-level design issues and how the computer is configured.
Computer Components
- Input
- Output
- Memory
- Datapath
- Control
Opening the Box
- Physical components of a computer (e.g., hard drive, processor, fan, memory, etc.).
Inside the Processor (CPU)
- CPU components:
- Datapath: performs operations on data.
- Control: sequences datapath, memory, and other components
- Cache memory: Small fast SRAM memory providing immediate access to data.
What is Under Your Program?
- Application software: written in a high-level language.
- System software:
- Compilers: translates high-level code into assembly code.
- Operating system: manages input/output, memory, and storage.
- Hardware: Processor, memory, etc.
Compilers and Assemblers
- Compiler: translates high-level language code into assembly code.
- Assembler: translates assembly code into machine code (0s and 1s).
Hardware
- Inputting data: Keyboard
- Outputting data: Speakers
- Processing data: Processor (Datapath & Control)
- Storing data: Cache
The Hardware/Software Interface
- Interface (ISA) between hardware and the lowest layer of software.
Summary
- A computer processes digital data.
- Users write programs using high-level languages; these programs are translated into assembly and binary code for execution.
- The compiled machine code operates on the five components of the CPU .
Performance
- Response Time (Execution Time): Time it takes to complete a task (important to users).
- Throughput (Bandwidth): Total work done per unit of time (important for datacenters).
Relative Performance
- Performance = 1/Execution time
- X is n times faster than Y: PerformanceX / PerformanceY = n
Measuring Execution Time
- Time, measured in seconds per program, is a crucial performance metric
- Elapsed time (response time/wall clock time) comprises processing, I/O (input/output), OS (operating system) overhead, and idle time.
- CPU time (CPU execution time) is the time spent processing a job.
CPU Clocking
- Digital hardware relies on a clock for timing
- Clock period: duration of a clock cycle (e.g., 250ps)
- Clock frequency: rate of cycles per second (e.g., 4.0GHz)
CPU Time
- CPU Time = CPU Clock Cycles × Clock Cycle Time
- Performance improves by reducing clock cycles and increasing clock rate.
CPU Time Example
Instruction Count and CPI
- Clock Cycles = Instruction Count × Cycles per Instruction (CPI)
- CPU Time = Instruction Count × CPI × Clock Cycle Time
- Instruction count for a program is determined by the program, ISA, and compiler.
- Average cycles per instruction (CPI) is determined by CPU hardware.
CPI Example
Weighted Average CPI
- Clock Cycles = ∑(CPIi × Instruction Counti)
- CPI = Clock Cycles / Instruction Count (Weighted average CPI)
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