Controller Circuitry and Algorithms

All modern drives include an integrated controller, also called its logic board, that functions as its "nerve center"; it runs the drive, controlling everything that happens within it. It also interfaces the drive to the rest of the PC system. The controller is discussed in this operation section.

The controller has an important but basically non-measurable impact on the overall performance of the hard disk. In some ways, I liken the controller of the hard disk to the umpires of a baseball game. One way of assessing how good a job the umpires are doing is as follows: if you don't notice that they are there, they are doing a good job; if you do notice them then maybe not. Similarly, the controller's job is to make sure everything happens as it should without drawing undue attention to itself.

The controller's speed in some ways affects the performance of everything in the drive simply because it manages everything in the drive. However, since it is much faster than the drive's mechanical components, its speed is shadowed by that of the slower components. The controller's design doesn't usually improve performance much, but if it is not designed to meet the needs of the other parts of the system, it can in theory harm performance. For example, when you are doing a sustained read from the drive, the controller cannot make the platters spin faster or affect the disk's recording density. It has no way to "speed up" the transfer, but if it is not designed to have enough capacity to handle the disk's maximum throughput, it can limit performance. Obviously, hard disk manufacturers make sure this doesn't happen.

Special algorithms within the controller, such as those used to manage multiple commands, can have a direct impact on performance under some types of usage.

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