Subject: Computer Organization and Architecture

Topic: Module 2

Difficulty: Low

MEMORY

• Computer data storage,often called storage or memory refers to computer components,devices,and recording media that retain digital data used for computing for some interval of time.
• Computer data storage provides one of the core functions of modern computer,ie,Information retention.
• So far,no practical universal storage medium exists,and all forms of storage have some drawbacks.
• Therefore a computer system usually contains several kind of storage each with individual purposes.

MEMORY CHARACTERISTICS

• The complex subject computer memory can be made manageable by classifying the memory systems according to their key characteristics.

• The most important characteristics are:-

  • Memory type
  • Memory size
  • Memory location
  • Word length
  • Addressable unit
  • Unit of transfer
  • Access method

THE MEMORY HIERARCHY

• The goal of any memory system is to provide adequate storage capacity with an acceptable level of performance and cost.
• One can achieve these goals by employing several memory types - with different cost/performance ratios-that are organized to provide a high average performance at a low average cost per bit.
• The objective of the organization is to achieve a good trade-off between cost,storage capacity and performance for the memory system as a whole.

• As one goes down the hierarchy,the following occur

  • Decreasing cost per bit
  • Increasing capacity
  • Increasing access time
  • Decreasing frequency of access of the memory by the CPU

• Thus smaller,more expensive memories are supplemented by larger,cheaper and slower memories.