CAO

• Computer system

  Architectural development and technological development
• Subject outcomes


  • Understand the architectural development of a computer system
  • Understand the technological development of a computer system
• Assessment criteria


  • CISC and the RISC architectural development and styles are discussed according to the prescribed material
  • The technological development in computer system is discussed according to the prescribed material
  • The performance of a computer is measured based on the time taken by a computer to execute a given job
  • The average number of clock cycles per instruction (CPI) is used to measure the performance
  • MIPS is used to measure the performance

  
• Assessment criteria


  • MIPS is used to measure the performance
  • Arithmetic and geometric means are used to summarize computer performance
  • The Amdahl's law for speedup is used to evaluate enhancement

  
• The computer industry are the result of a long chain of immense and successful efforts made by two major forces: the academia, represented by university research centers, and the industry, represented by computer companies
• Computer systems


  Conventionally defined through their interfaces at a number of layered abstraction levels, each providing functional support to its predecessor. Included among the levels are the application programs, the high-level languages, and the set of machine instructions
• Computer architecture


  Built on four basic viewpoints: the structure, the organization, the implementation, and the performance
• Structure


  Defines the interconnection of various hardware components
• Organization


  Defines the dynamic interplay and management of the various components
• Implementation


  Defines the detailed design of hardware components
• Performance


  Specifies the behaviour of the computer system
• CISC


  Complex instructions set computers, where the philosophy is to do more in less instruction
• Increasing the complexity of instructions and the number of addressing modes has the theoretical advantage of reducing the "semantic gap" between the instructions in a high-level language and those in the low-level (machine) language
• RISC


  Reduced instructions set computers, where the philosophy is to promote the optimization of architectures by speeding up those operations that are most frequently used (assignment statements, conditional statements) while reducing the instruction complexities and the number of addressing modes
• It was increasingly difficult to support higher clock rates because of the increased complexity of computations within a single clock period
• RISC machines


  • Sun SPARC and MIPS machines
• There is an unending and unresolved controversy over whether RISC or CISC is the best
• RISC architectures would indeed lead to faster execution of programs, and the majority of contemporary microprocessor chips seems to follow the RISC paradigm
• Technological development


  The continuous decrease in the minimum devices feature size has led to a continuous increase in the number of devices per chip, which in turn has led to a number of developments
• Clock cycle time


  The time between two consecutive rising (trailing) edges of a periodic clock signal

  
• Performance analysis


  Helps answer questions such as how fast can a program be executed using a given computer
• Facets of computer performance

  • Time taken to execute an instruction (user side)
  • Total amount of work done in a given time (laboratory side)
• CPI (average number of clock cycles per instruction)

  Computed by dividing the total number of clock cycles by the total number of instructions executed

  
• MIPS (million instructions-per-second)


  The rate of instruction execution per unit time

  
• Arithmetic mean


  Used to summarize performance regarding larger sets of programs (e.g., benchmark suites)
• Geometric mean


  Used to summarize performance regarding larger sets of programs (e.g., benchmark suites)
• Example of MIPS calculation

  • Given: CPU clock rate = 1 GHz, CPI = 2, then MIPS = 500

  
• Amdahl's law for speedup is used to evaluate enhancement

  
• Mostafa Abd-El-Baar and Hesham El-Rewini: 'Fundamentals of computer organization and architecture'