Trends in non-software support for input-output functions

Input-output subsystem architectures have evolved over the past 20-odd years to the point where two divergent approaches have found acceptance in current computer systems; the 'IBM channel' is the archetype of the lower level alternative, while the functionally more complex techniques involve a wide spectrum of distributed processor architectures supporting database and/or storage management functions independently with respect to the central processor. The paper traces the historical development of support (outside central processor based software) for input-output functions and concludes with a preliminary comparison of the relative merits of the software interfaces provided by the alternative input-output subsystem architectures.