Computer Architecture: Introduction to Digital Processes, Lecture notes of Advanced Computer Architecture

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COMPUTER ARCHITECTURE

(Part1:Digital Processes)

Introduction to Computer Architecture

1 Concept of computer architecture

2 Computer performance

2 Instruction set architecture

The instruction set is a critical interface between

software and hardware.

Software Instruction Set Hardware

This includes

• Instruction Set (what operations can be performed?)
• Instruction Format (how are instructions specified?)
• Data storage (where is data located?)
• Addressing Modes (how is data accessed?)
• Exceptional Conditions (what happens if something goes wrong?)

3 Machine organization

Machine organization is the view of the computer that

is seen by the logic designer. This includes

• Ways in which these components are interconnected
• Capabilities & performance characteristics of functional units (e.g., registers, ALU, shifters, etc.).
• How information flows between components
• Logic and means by which such information flow is controlled
• Coordination of functional units to realize the ISA

Typically the machine organization is designed to meet a given instruction set architecture. However, in order to design good instruction sets, it is important to understand how the architecture might be implemented.

- Memory (instructions, data) Control Datapath registers ALU, buses CPU Computer System Input Output I/O Devices --Central Processing Unit (CPU): Control Unit (instruction decode, sequencing of operations), Datapath (registers, arithmetic and logic unit, buses). --Memory: Instruction and operand storage. --Input/Output (I/O). --The stored program concept: Instructions from an instruction set are fetched from a common memory and executed one at a time.

Hardware Components of Any ComputerHardware Components of Any Computer

Processor (active) Computer Control Unit Datapath Memory (passive) (where programs, data live when running) Devices Input Output Keyboard, Mouse, etc. Display , Printer, etc. Disk Five classic components of all computers: Five classic components of all computers:

1. Control Unit; 2. Datapath; 3. Memory; 4. Input; 5. Output 1. Control Unit; 2. Datapath; 3. Memory; 4. Input; 5. Output

Processor

Computer Architecture Vs. Computer OrganizationComputer Architecture Vs. Computer Organization

• (^) The term Computer architecture is sometimes erroneously restricted to computer instruction set design, with other aspects of computer design called implementation.
• (^) More accurate definitions:
  • (^) Instruction set architecture: The actual programmer-visible instruction set and serves as the boundary between the software and hardware.
  • (^) Implementation of a machine has two components:
    • (^) Organization: includes the high-level aspects of a computer’s design such as: The memory system, the bus structure, the internal CPU unit which includes implementations of arithmetic, logic, branching, and data transfer operations.
    • (^) Hardware: Refers to the specifics of the machine such as detailed logic design and packaging technology.
• (^) In general, Computer Architecture refers to the above three aspects: 1- Instruction set architecture 2- Organization. 3- Hardware.

Computer Performance

1 Performance and Cost

• Purchasing perspective given a collection of machines, which has the ---- best performance? ---- least cost? ---- best performance / cost?

2 What is performance?

When we say one computer has better performance than another, what do we mean? There are two main measures of performance, execution time and Throughput. For an individual computer user, you are interested in reducing response time For computer center managers, they are interested in increasing throughput —the time between the start and completion of a task--- also referred to as execution time. —the total amount of work done in a given time.

Response Time (latency) Throughput How long does it take for my job to run? How long does it take to execute a job? How long must I wait for the database query? How many jobs can the machine run at once? What is the average execution rate? How much work is getting done?

Performance Definition Performance is units of things-per-second. (the bigger the better) If we are primarily concerned with response time

_ ( )

execution time x

performance x 

X is n times faster than Y: n = Performance (X) /Performance (Y) = execution_time(Y)/execution_time(X)

Example: If an Pentium III runs a program in 8 seconds and a PowerPC runs the same program in 10 seconds, how many times faster is the Pentium III? n = 10/8 = 1.25 times faster (or 25% faster) X is n times faster than Y: n = Performance (X) /Performance (Y) = execution_time(Y)/execution_time(X)