Abstract: In a buffered data storage subsystem, data is promoted to the buffer in anticipation of a connected host using the promoted data in the near future. In a tape recorder data storage apparatus the actual position of the tape reflects the last promoted data; such actual tape position is "inconsistent" with host operations. If the sequence of host operations continues, such inconsistency actually enhances total operations. When the subsystem detects a change or possible change in future host operations (rewind command, change in tape motion direction, etc.), detect end of file (tape mark) or a change in subsystem operations (load balance affecting drive or deallocation of buffer from drive) the data promoted to the buffer and not read by the host is erased from the buffer. The tape is moved such that upon a forward motion the tape drive would next read data on tape corresponding to the data block erased from the buffer.

Abstract: A peripheral system has one or more buffered control units connected to a plurality of peripheral devices. Operation times of the devices are marked by the buffer and controls which overlap device operations, queue device operations in a priority set of queues, and prioritize peripheral system operations. Plural specialized interconnections between each control unit and the devices include a preparatory connection for transfer of preparatory commands to devices, a tag or control connection for device selection, deselection and control and a data-command connection for signal transfers between a selecting control unit and a selected peripheral device.