Abstract: The method and apparatus in a microprocessor-based data processing system which allows direct access to main memory associated with a central processing unit from peripheral intelligent devices such as mass storage and special processors. Main memory space is allocated in contiguous zones of actual memory and "phantom" memory. An address decoder in connection with a bus buffer separates the peripheral from the CPU or the CPU from the peripheral whenever particular instructions are generated or address space is selected. During direct memory access, the CPU is placed in an idle state without disturbing CPU registers so that secondary functions of the CPU can be continued. The method and apparatus eliminates need for a conventional direct memory access device with its undesirably high overhead and support requirements.

Abstract: A magnetic disc drive system having a pair of vertically spaced discs rotatably mounted in a compact housing provided with a cover for closing the housing. The cover has a duct extending along its inner surface for performing part of an air flow path through the housing. An impeller mounted above the upper discs rotates with the discs and generates the air flow which moves outwardly off the discs to keep the surfaces of the discs free of foreign particles. The air flow path extends downwardly past the discs and along the bottom of the housing and into a cavity which contains a filter which traps foreign particles. The upper end of the filter is coupled in a sealing relationship to one end of the duct to complete the air flow path. A number of read-write heads are mounted on a shiftable carriage and are coupled with the discs for movement back and forth along the discs in response to signals applied to a reversible motor coupled to the carriage.

Abstract: An improved motor assembly including a brushless D.C. motor and an annular member defining a platform for the drive electronics and speed control circuits of the motor. The member is carried on a fixed support within the outer envelope of the motor and includes a thin disk-like body providing a pair of opposed surfaces for mounting the components of the circuits. The fixed support of the motor has a flat annular face surrounding the drive shaft of the motor, and the annular member engages and is secured to the flat face of the support in surrounding relationship to the shaft. In a preferred embodiment, the housing of the motor defines part of the rotor of the motor and is for rotation with the shaft. A flange is secured to the support near the opposite end of the shaft for mounting the motor on a fixed support, such as on the base of a housing forming a part of a disk drive unit.

Abstract: A disk drive unit having a housing provided with an upper region, a lower region, and a central region between the upper and lower regions. The upper region contains one or more rotatable memory disks, and the central region communicates with the upper region and contains a drive motor, the upper and central regions being closed to the atmosphere. The disks are coupled to a rotatable hub in the upper region and the hub has an improved jam screw for securing it to one end of the drive shaft of the drive motor so that the disks can be rotated at high speeds. One or more read-write heads can be used with each disk, respectively, and a linear motor coupled with each head moves the latter radially of the corresponding disk in accordance with control signals applied to the linear motor.