Hard disk logic board control circuitry sense amplification conversion circuits interface hardware firmware multiple command control reordering PC hard disks IDE Integrated Drive Electronics SCSI Small Computer Systems Interface ATA


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Logic Board

The newer hard disks drives have been introduced with a lot of features and faster speed in it and development is still on progress. To control all these functions and provide the disk’s high performance features in advanced way in which they are expected to be, all modern hard disks are made with an intelligent circuit board integrated into the hard disk unit. This circuit board is called Hard Disk Logic Board. A logic board uses its following important components to provide a variety of functions and features to a hard disk:

  • Control Circuitry
  • Sense, Amplification and Conversion Circuits
  • Interface Hardware
  • Firmware
  • Multiple Command Control and Reordering

Both of The two most common interfaces popular today for PC hard disks IDE (Integrated Drive Electronics) and SCSI (Small Computer Systems Interface) use integrated controllers. The more correct name for the IDE interface is AT Attachment or ATA (Advanced Technology Attachment). The modern hard disks have a very sophisticated logic board which contains more memory and faster internal processors than an entire PC of even the mid-1980s.

The logic board performs several important functions then before. Therefore the logic circuits needs to be more powerful, to handle changes like geometry translation, advanced reliability features, more complicated head technologies, faster interfaces, and higher bandwidth data streaming from the disk itself.

The internal logic board of a hard disk contains a microprocessor and internal memory, and other structures and circuits that control what happens inside the drive. Some of the most important functions of the control circuitry of the drive are as follows:

  • Controlling the spindle motor, including making sure the spindle runs at the correct speed.
  • Controlling the movement of actuator to various tracks.
  • Managing all read and write operations.
  • Implementing power management features.
  • Handling geometry translation.
  • Managing the internal cache and optimization features such as pre-fetch.
  • Coordinating and integrating the other functions mentioned in this section, such as the flow of information over the hard disk interface, optimizing multiple requests, converting data to and from the form the read/write heads require it, etc.
  • Implementing all advanced performance and reliability features.

The modern hard disks have internal microprocessors and most of them also have internal software that runs them. These routines run the control logic and make the drive work. In fact this is not really software in the conventional sense, because these instructions are embedded into read-only memory. This code is analogous to the system BIOS, low-level, hardware-based control routines, embedded in ROM. It is usually called firmware.

This is the reason why sometimes Firmware is called the middle link of hardware and software. In many drives the firmware can be updated under software control.

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