Memory Architecture

• Memory Architecture

  • Storage Function
  • Main Storage Unit (RAM) - volatile
  • Auxiliary Storage Devices (ROM) - non-volatile

  1. Hard disks
  2. Magnetic Tape
  3. Floppy disk
  4. Magneto-optical disk
• Magnetic Disk Unit

  • Devices that store data using magnetic disks.
  • Most widely used auxiliary storage device.
• • Magnetic disks for personal computers or workstations are also called fixed disks or hard disks but the mechanism is the same.
• Magnetic Media: Tracks, Cylinders, CD ROM, DVD
• The term 'magnetic media' is used to describe any record format where analogue or digital information is recorded to and retrieved from a coated matrix that can be magnetised.
• Tracks

  • Data recorded along rings are called tracks.
  • Length of the outer tracks are larger than that of the inner tracks.
• Cylinders

  • In magnetic disk units
  • Multiple magnetic disks
  • Groups of tracks with the same radius on each of the disks as one data storage are called a ‘cylinder’.
• CD ROMS

  • Compact disc read only memory
  • Can contain text, graphics, and videos as well as sound.
  • Cannot be erased or modified
  • Use CD-ROM drive or CD-player to read
  • Used to distribute software
  • Spiral compared to track. Through laser
• DVD

  • Digital Versatile Disk or Digital Video Disk
  • Capable of storing up to 2 hours (or more depending on standard used) of animated images and audio data.
  • Can be thought of as layering CD-ROMs one on top of the other.
• The computer memory can be divided into 5 major hierarchies that are based on use as well as speed. A processor can easily move from any one level to some other on the basis of its requirements. These five hierarchies in a system's memory are register, cache memory, main memory, magnetic disc, and magnetic tape.
• Register - 100 bytes
• Cache Memory - 100 kilobytes
• Main Storage Unit - 10 to 100 mega bytes
• Disk Cache - 100 m to 1 giga bytes
• Magnetic disk unit - over tens of m bytes to 100 giga bytes
• The concept of memory capacity usually refers to the amount of information that can be held in the short-term store (STS) and has been typically assessed via memory span tasks or measures of working memory.
• Kilobyte = 1 thousand bytes = 1024 bytes = 50 pages of text
• Megabyte = 1 million bytes = 1,048,576 bytes = 50,000 pages
• Gigabyte = 1 billion bytes = 1,073,741,824 bytes = 50,000,000 pages
• Terabyte = 1 trillion bytes = 1,099,511, 627, 778 bytes = 50,000,000,000 pages
• Auxiliary storage is any storage that is made available to the system through input/output channels. This term refers to any addressable storage that is not within the system memory (RAM). These storage devices hold data and programs for future use and are considered nonvolatile storage that retains information even when power is not available. They trade slower read/write rates for increased storage capacity. May also be referred to as secondary storage.