According to an embodiment, a magnetic disk device includes a magnetic disk, a spindle motor that rotates the magnetic disk, a motor driver, and a controller. The motor driver supplies a motor current to the spindle motor and measures a counter electromotive voltage of the spindle motor every time the spindle motor makes one rotation. After the rotation of the magnetic disk starts, the controller adjusts a motor position where the counter electromotive voltage is measured to a set first position.

According to an embodiment, a magnetic disk device includes a magnetic disk, a spindle motor that rotates the magnetic disk, a motor driver, and a controller. The motor driver supplies a motor current to the spindle motor and measures a counter electromotive voltage of the spindle motor every time the spindle motor makes one rotation. After the rotation of the magnetic disk starts, the controller adjusts a motor position where the counter electromotive voltage is measured to a set first position.

Various illustrative aspects are directed to a data storage device comprising a first spindle motor configured to rotate one or more disks in a first stack of disks, a second spindle motor configured to rotate one or more disks in a second stack of disks, and one or more processing devices configured to detect back electromotive force (BEMF) voltages generated by the first spindle motor and the second spindle motor. In other aspects the one or more processing devices can control speeds of the first spindle motor and the second spindle motor based on the detected BEMF voltages.

A server box embodiment is disclosed that generally comprises an array of dummy HDDs that share a common set of universal disk drive components in a master components module, or power module. Each dummy HDDs is constructed without expensive onboard chipsets that control the normal functionality of a standard HDD. By sharing expensive chipsets in a master components module (power module) money can be saved in building and selling the dummy HDD server. Embodiments envision a power module possessing the needed chipset functionality that is missing in a dummy HDD. The power module can be made to move from dummy HDD to dummy HDD supplying the necessary chipset in a shared manner when data is being stored or retrieved for client or end-user.

A server box embodiment is disclosed that generally comprises an array of dummy HDDs that share a common set of universal disk drive components in a master components module, or power module. Each dummy HDDs is constructed without expensive onboard chipsets that control the normal functionality of a standard HDD. By sharing expensive chipsets in a master components module (power module) money can be saved in building and selling the dummy HDD server. Embodiments envision a power module possessing the needed chipset functionality that is missing in a dummy HDD. The power module can be made to move from dummy HDD to dummy HDD supplying the necessary chipset in a shared manner when data is being stored or retrieved for client or end-user.

A control device (1) is configured to reduce the commutation angle error ε of a three-phase (u, v, w) EC motor (2.2) connected via a y-configuration. The three phases (u, v, w) are commutated via a motor control (3) including a rotor position sensor (4) and a control circuit (10). The rotor position sensor (4) senses the relative angular position of the rotor using the neutral-point potential at the neutral point of the y-configuration. The control circuit (10) is configured to impose a desired field weakening current component on the motor control (3) for reducing the commutation angle error ε.

According to an embodiment, a magnetic disk device includes a magnetic disk, a spindle motor that rotates the magnetic disk, a motor driver, and a controller. The motor driver supplies a motor current to the spindle motor and measures a counter electromotive voltage of the spindle motor every time the spindle motor makes one rotation. After the rotation of the magnetic disk starts, the controller adjusts a motor position where the counter electromotive voltage is measured to a set first position.

According to an embodiment, a magnetic disk device includes a magnetic disk, a spindle motor that rotates the magnetic disk, a motor driver, and a controller. The motor driver supplies a motor current to the spindle motor and measures a counter electromotive voltage of the spindle motor every time the spindle motor makes one rotation. After the rotation of the magnetic disk starts, the controller adjusts a motor position where the counter electromotive voltage is measured to a set first position.

A comparator circuit with a speed control element is disclosed herein. The speed control element may include a variable voltage source and one or more transistors. Using a voltage supplied by the variable voltage source, the one or more transistors may control a swing of a clock signal to provide a swing controlled clock signal to an amplification portion of the comparator circuit. The swing controlled clock therefor may be used to control the speed of the comparator circuit (e.g., an amplification phase) based on a level of noise in the circuit. The swing controlled clock may further be used to align an output common voltage of the comparator circuit with switching voltages of downstream logic cells (e.g., inverters) connected to the comparator circuit.

Various illustrative aspects are directed to a data storage device comprising a first spindle motor configured to rotate one or more disks in a first stack of disks, a second spindle motor configured to rotate one or more disks in a second stack of disks, and one or more processing devices configured to detect back electromotive force (BEMF) voltages generated by the first spindle motor and the second spindle motor. In other aspects the one or more processing devices can control speeds of the first spindle motor and the second spindle motor based on the detected BEMF voltages.