A small part of the firmware of the controller is stored in a chip, and the rest is stored on magnetic disks in the service area specially taken away for this purpose. This area is unavailable to the user. After feed of an operating voltage or activation of a "reset" signal on the informational bus the hard drive microprocessor restarts the program written in a chip, fulfils self-test, tests the random access memory, programs the chips which are on the internal bus of a hard disk drive, and in the absence of an contingency starts the engine. Then, measuring the period of movement of impulses of phase windings, it waits until the engine gains the rated rotation speed. After that it orders to move the magnetic heads to the track containing the firmware and starts to read out the servo marking, finally stabilizing the speed of rotation. After reading of the firmware and its subsequent performance the hard drive is ready to receive the signals from the computer front-end interface.
Performance and reliability of the HDD depend on efficiency and quality of the internal software executed by the microprocessor of the disk drive. Many manufacturers constantly adjust the firmware, improving its functional parameters during all the time of the certain model of the disk drive production. Almost all hard drives allow users, in the presence of the special software, to refresh the microcode, but, as a rule, there is no such a necessity as the serious errors which can prevent the firmware of modern storage devices from normal operation do not happen. Furthermore, any failure at upgrade can lead to complete non-operability of the disk drive. After the upgrade, it is not reasonable to expect any significant changes and improvements in the operation of a HDD and there is even less sense to hope for the occurrence of additional functions or appreciable increase in productivity since the upgrades are usually intended only to increase the reliability of hard drives operation.