Abstract: A method and apparatus for storing compressed data on DAT media. The data is stored into a standard DDS group format prior to compression, and after compression, the group is stored into a variable number of frames for recording onto the DAT media. If the compression does not meet a predetermined standard of efficiency, then the group is stored in a fixed number of frames and recorded onto the DAT media without compression.

Abstract: A streaming tape drive for use in computer systems for the storage and retrieval of data on magnetic tape has the capability of locating a selected block of data stored on magnetic tape in serpentine fashion by first moving the magnetic head of the tape drive from one data track to another data track until the head is positioned to a data track which has a data block having a block number that is within a predetermined numeric value of the block number of the selected data block for which tape drive is searching. After the head is so moved to the data track, the tape drive performs a sequential search of the tape on a block-by-block basis until the selected data block is found. The tape drive has the capability to perform such searches on magnetic tape that is recorded in standard serpentine fashion, and no special tape recording format is required.

Abstract: There is shown and described a method and apparatus for using a "block move" instruction in a microprocessor to execute the direct memory access (DMA) data transfer function between a microprocessor and a minicomputer. The instruction permits an apparent data transfer in the memory of the microprocessor to be utilized to transfer data to the memory in the minicomputer. Little or no additional hardware over existing systems is required.