PC CONTROLLER DEVICES
Any device on a computer will have a "controller" device, whether it is on the motherboard, or inserted into an expansion slot in the form of a PC card. Many PCs have the controllers built into the mother board for devices such as IDE disk controller, printers, etc. An electrical cable (usually a parallel(ribbon) cable) attaches the hardware devices to the controller. Each type of device uses their own encoding scheme

Encoding Schemes - When reading a Hard disk, the read head can only detect changes in the magnetic field or flux reversals. An encoder/decoder converts digital signals from the data bus into a waveform that will place these flux reversals on the disk surface. The process reverses during a data read. Sme of the older methods used to encode/decode information on a disk are:

  • Modified Frequency Modulation.

  • RLL - Run Length Limited

  • ARLL - Advanced Run Length Limited

Disk Interfaces In the world of data recovery, it helps to know a little about the disk interface you are working with, because quite a few data recovery problems are a direct result of drive set-up and installation problems.

The main job of the disk interface (or controller) is to transmit, receive, and interpret data sent to and from the drive.

If you are building or upgrading a system with performance in mind, you need to have a good knowledge of the different effects each type of interface has on performance.

In order for the computer to understand the data recorded on the hard drive, the interface must be able to decode current flow signals into useful information.

  • Electronic circuits in a drive interface amplify and decode these current flow signals into digital signals used by the computer to represent data.

  • The method used to encode or decode data signals varies depending on the type of drive you have. Different disk encoding schemes use different disk interface / controller combinations.

History of Interface Development
The last few years has seen the development of four major disk interface configurations. The type of interface used limits how fast data can be moved from the drive to your computers' memory.

Each interface type requires a different installation and set-up procedure. Special problems can arise when you are trying to add two or more drives to a system. Especially when you are using, two different types of drive interfaces.

The type of controllers listed above primarily control the interface of storage devices to the motherboard's bus such as an ISA, EISA, or even a PCI bus.

There are other types of controllers on chips in the computer that you may not even know about or be able to see. For example 'memory controller', VL Bus controller, PCI bus controller.

Some "expansion" cards even act in a 'controller' function and perform other functions as well.etc. An example is a video adapter card, or a video accelerator card.