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1.2 Hardware Structure
The HDDs have a disk enclosure (DE) and a printed circuit board assembly (PCBA). The DE
includes the heads on an actuator and the 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 of 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 of
servo information in the data.
The heads are positioned on the ramp when the power is off or the spindle motor is stopped.
(5) Air circulation (recirculation filter, breather filter)
The disk enclosure (DE) configures a clean room to keep out particle and other contaminants.
The DE has a closed-loop air recirculation system. Using the movement of the rotating disks, air
is continuously cycled through a filter. This filter will trap any particle floating inside the
enclosure and keep the air inside the DE contaminant free. To prevent negative pressure in the
vicinity of the spindle when the disks begin rotating, a breather filter is attached. The breather
filter also equalizes the internal air pressure with the atmospheric pressure due to surrounding
temperature changes.
(6) 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.
(7) 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 SCSI controller.
18 C141-E270