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1.2 Hardware Structure
C141-E252 17
1.2 Hardware Structure
The HDDs have a disk enclosure (DE) and a printed circuit board assembly (PCBA). The DE
includes heads on an actuator and disks on a spindle motor mounted on the DE. The PCBA includes
a read/write circuit and a controller circuit.
(1) Disks
The disks have an outer diameter of 70 mm (2.8 inch).
(2) Heads
The heads have MR (Magnet – Resistive) read element Ramp Load type slider.
(3) Spindle motor
The disks are rotated by a direct-drive hall-less DC motor. The motor speed is controlled by a
feedback circuit using the counter electromotive current to precisely maintain the specified speed.
(4) Actuator
The actuator, which uses a rotary voice coil motor (VCM), consumes little power and generates little
heat. The heads at the end of the actuator arm are controlled and positioned via feedback servo loop.
The heads are positioned on the ramp when the power is off or the spindle motor is stopped.
(5) Read/write circuit
The read/write circuit utilizes a read channel mounted with a head IC that supports high-speed
transmission and an MEEPRML (Modified Enhanced Extended Partial Response Maximum
Likelihood) modulation/demodulation circuit in order to prevent errors being triggered by external
noise and to improve data reliability.
(6) Controller circuit
The controller circuit uses LSIs to increase the reliability and uses a high speed microprocessing unit
(MPU) to increase the performance of the SAS controller.