Secondary Memory Storage Devices

CPU Register Memory Usage

• Function of CPU Registers:
  • Data and instructions must be loaded into registers before they can be processed by the Central Processing Unit (CPU).
  • This memory is specially utilized by the CPU to process incoming data and prepare output results.

Secondary Memory and Mass Storage Devices

Hard Disk Drive (HDD)

• Overview and Terminology:

  • Also commonly referred to as a hard drive or hard disk.
  • Serves as the primary main storage device in a computer system.
  • Designated as a hard drive because both the data-storing disk and the data read/write components are combined together within a single physical unit.

• Physical Housing and Platter Composition:

  • Located within a dedicated drive unit and composed of one or more platters packed in an air-sealed casing.
  • Incorporates $2$ to $4$ metallic disks (platters).
  • Material Construction: Disks are typically manufactured from aluminum.
  • Surface Coating: Each data-storing surface is coated with a layer of magnetic oxide.
  • Usable Storage Surfaces: Both sides of each platter are utilized for storing data, with two explicit exceptions:
  • The upper side of the uppermost disk is not used for storage.
  • The lower side of the lowermost disk is not used for storage.

• Read/Write Operations and Speed:

  • Each active data-storing surface contains its own separate read/write head.
  • Data is written onto the platters by moving a magnetic head over the surfaces as the platters spin.
  • During data read and write processes, platters rotate at speeds between $3600\text{ rpm}$ and $15000\text{ rpm}$ (revolutions per minute).

• Storage Capacity and Contents:

  • Storage capacity ranges from a few Mega Bytes ($\text{MB}$) up to Terra Bytes ($\text{TB}$).
  • Typical data stored on a computer's hard drive includes:
  • The operating system
  • Installed software and programs
  • User files and pictures
  • Music files
  • Video files
  • Text documents

Solid State Disk (SSD)

• Definition and Function:

  • A type of mass storage device functionally similar to a hard disk drive (HDD).
  • Supports reading and writing data while maintaining all stored data in a permanent, non-volatile state.

• Internal Architecture:

  • Internal components are fundamentally different from mechanical hard drives.
  • SSDs contain no moving parts, unlike traditional hard drives.

• Interface and Connectivity:

  • Internal SSDs connect to a computer system using standard interface connections identical to those used by hard drives:
  • IDE: Integrated Drive Electronics
  • SATA: Serial Advanced Technology Attachment