Hitachi, Ltd.

Hitachi Computer Peripherals Co., Ltd.

Toshiyuki Haruna

Akira Kojima

Tsuneo Hirose

Masahiko Sato

Katsuhiro Tsuneta

Tetsuzo Kobashi

Yuji Yoshida

Akira Ishibashi

Hiroshi Masuda

Hiroshi Nishida

Akira Kurano

Hideaki Amano

Kazuo Nakagoshi

Kiyotaka Takahashi

Kenji Nishimura

Asao Sasamoto

Norikazu Takayama

Yoshinobu Kudou

Motohiro Nakai

Nobuyoshi Ushijima

Masahiko Satou

Riichi Nakano

Kazuto Takahashi

Tadayuki Ichiba

A rotary storage device includes a plurality of disk units, an upper-level interface circuit, a cache controller, a cache memory, and a control processor. In each disk unit, the storage area of each disk is subdivided into an ordinary user data area and a secondary cache data storage area including a group of consecutive cylinders. Data overflowed from the cache memory is sequentially written in the secondary cache data storage area so as to be later transferred therefrom to areas of the user data area according to addresses inherent thereto when traffic of upper-level input/output processing is relatively low. In the case of when data is sought to be accessed in the cache memory during a data read operation, access operations are performed first to the secondary cache data storage area and then to the user data area.

Rotary memory storage device with cache control method and apparatus

A cache control method and a rotary storage device are capable at a low cost, of improving the hit rate and minimizing the processing time in the event of a miss hit. The rotary storage devices includes a plurality of disk units, an upper-level interface circuit, a cache controller, a cache memory, and a control processor. In each disk unit, the storage area of each disk is subdivided into an ordinary user data area and a secondary cache data storage area including a group of consecutive cylinders. Data which has overflowed from the cache memory is sequentially written in the secondary cache data storage area so as to be later transferred therefrom to areas of the user data area according to addresses inherent thereto when traffic of upper-level input/output processing is relatively low. In the case of a miss hit of the cache memory during a data read operation, access operations are performed first to the secondary cache data storage area and then to the user data area.

Cache control method and rotary storage device having cache control

A head positioning device for use in a magnetic disk equipment includes a position detector for detecting the deviation of a magnetic head from the center line of a desired track on a magnetic disk, a comparator for generating a polarity signal indicative of the direction of the deviation of the magnetic head from the center line of the desired track, on the basis of the output of the position detector, and a microcomputer for calculating a correction value necessary for the precise positioning of the magnetic head on the center line of the desired track. An optimum correction value is determined for each of a plurality of tracks on the basis of measurement, immediately after the power supply of the magnetic disk equipment has been turned on, and an actuator mounted with the magnetic head is driven on the basis of the correction values thus obtained, to position the magnetic head very accurately.

Head positioning device for use in magnetic disk equipment

A control method for brushless DC motor having a rotor, a plurality of magnetic poles and coils of a plurality of phases involves sequentially applying a current to one phase for a prescribed time, stopping the current temporarily and then reapplying the current to the same phase. The state of the rise of the current when it begins to flow to the phase, is measured. The position of one of the magnetic poles located at a position opposite to the particular phase is detected based on the measured state of the rise of the current. In response to the position of the magnetic pole, it is determined whether the flow of the current is to be switched over to the following phase or not. If so, the current is switched over the following phase and the process is repeated. Constant speed control may be accomplished by reading information from a driven disk to determine speed, comparing the speed to a fixed speed, and selectively applying by time sharing a normal current, a brake current and an acceleration current.

Control system for brushless DC motor

In a magnetic disk unit for recording/reproducing data onto/from a disc by means of a magnetic head on the basis of a seek command and a recording/reproducing command received from a host processor, the execution of the data reproducing command for the disk is started upon detection of a state that the magnetic head has sought on a desired track to an extent that the centering state is still unstable but the data can be reproduced, and the execution of the data recording command is started upon detection of a condition that the magnetic head has reached the stable centering state on the desired track after the detection of the reproducible state.

Recording/reproducing method and apparatus of magnetic disk unit in

A magnetic disc unit capable of improving the throughput by minimizing the seek time for the magnetic head. The magnetic disc unit is operative to respond to a cylinder address instructed by the host unit to move the magnetic head to the corresponding cylinder position on the magnetic disc comprises a cylinder address/position assignment selecting circuit for changing the address instructed by the host unit into a new address so as to desirably change cylinder address/position assignments. A head location controlling circuit is responsive to the new address to move the magnetic head to a cylinder position corresponding to the new address. In one mode, the cylinder address/position assignment selecting circuit performs renewal of cylinder addresses such that the magnetic head passes along the magnetic disc through all of the cylinder positions designated by cylinder addresses by making a return trip between inner and outer circumferences of the magnetic disc. In another mode, the cylinder address/position assignment selecting circuit performs renewal of cylinder addresses that when the innermost cylinder address is substituted for a cylinder address instructed by the host unit, the access time for the substitutive cylinder address is minimized.

Magnetic disc unit system

In a magnetic disc memory apparatus in which a magnetic head is in contact with a surface of a magnetic disc when the disc is stationary and caused to float upon rotation of the disc, the magnetic head contacting the magnetic disc is slightly moved in the radial direction of the disc immediately before rotation of the disc, whereby the rotation of the magnetic disc is started after adhesion between the magnetic disc and the magnetic head has been obviated.

Apparatus for reducing starting adhesion between a magnetic disc and

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Odawara, Japan

Toshiyuki Haruna