Abstract: A central sub-system of a data processing system, including an operator console controlling a service processor, is divided into several sub-units, functioning separately from each other. The sub-units include processors that are connected together and to a common controller for a common memory unit by data, address and control buses. Each sub-unit includes a configuration device that stores an appurtenance indicator derived from the service processor in response to sub-unit initialization, and enables its associated sub-unit to exchange data with the memory unit. The sub-unit having the highest priority of the sub-units attempting to access the memory units is connected to the memory unit by the controller. A single configuration memory stores an indication of the sub-units in service in the central sub-system. The configuration memory is addressed each time the memory unit is addressed by a signal indicative of the appurtenance indicator derived from the selected sub-unit.

Abstract: A data processing system includes apparatus for addressing operands within a segment utilizing segment descriptors. The apparatus is responsive to instruction words executed by a first of a plurality of processes.

Abstract: The disclosure describes improved apparatus and method for implementing the test of various computer functional units interconnected by a common bus. At the beginning of the method, each functional unit is subjected to an enforced condition which disconnects it from the bus. Then, one of the units is subjected to an enforced condition which connects it to the bus and is tested under microprogram control. After the one unit has been tested, another unit is connected to the bus and is tested. In this manner the functional units after first being disconnected from the common bus are reconnected and tested one at a time and those units which have no error detected therein are maintained connected.