Slotting Allowances and Antitrust

A microprogrammable peripheral controller is provided in which the control store microinstruction format is compatible with the read/write memory data word format and the architecture is compatible with character oriented peripheral data formats. The controller is provided with a processor which enables word transfers in a single operation. The processor also has the capability of performing a large repertory of arithmetic and logic microinstructions, but this is made economical by limiting such operations, in general, to byte length operands. With this processing capability, the primary controller control functions can be performed economically for a wide range of perioherals. A common interface is provided for data and control information transfers between the controller and both peripheral devices and central processor ports. In general, adaptor units are required to provide compatibility between the controller and the CPU ports and peripheral interfaces, to provide data buffering, to support multiplexing and for any other special functions. The primary feature to which this disclosure is directed is processor architecutral features which effectively eliminate processor execution time for performing branching operations whereby processing speed is effectively increased by a factor of more than one third for many if not all control store programs. Controller economy and reliability is further advanced by the use of dual arithmetic/logic modules which serve as redundant elements for byte operations and word transfer elements for word transfer operations.