Abstract: A method and means for efficiently utilizing bus bandwidth among processors and input/output devices burst coupled in master/slave pairs over a clocked, arbitrated, bidirectional, multistate, local communications bus. The method resynchronizes arbitrated masters and selected slaves perturbed during their bus-coupled transactions by recirculating data during a write operation at a bus master in the absence of a slave acceptance signal, or recirculating by a slave in the absence of a master response. The recirculating master or slave responsive to a delayed indication from its passive opposite then sends out the data over the bus at an integral multiple of the clock rate.

Abstract: A multi-node data processing system implements a method that assures that plural messages are enabled "fair" access to a data stream. Each node includes apparatus for controlling message transmissions and/or receptions from another node over a communication network. The method comprises the steps of: transmitting a routing message from a first destination node to a source node, the routing message signalling a readiness of the destination node to receive a data message; transmitting a first data message to the first destination node from the source node in response to the ready message; transmitting a conditional disconnect message from the first destination node to the source node upon receipt of a predetermined amount (i.e. a "slice") of the first data message.

Abstract: Apparatus and method for optimizing bus arbitration during direct memory access (DMA) data transfers across a nondedicated bus between a memory and/or a plurality of external devices each master having an arbitration priority. At least two nonoverlapping clocks are provided per transfer cycle and there is at least one transfer cycle per arbitration cycle. Arbitration priority requests are transmitted from each external device to an arbitration bus only at the rise of the first clock. At the end of the last clock, the priority code of the external device having the highest priority is determined to designate the external device which is to become bus master. Addresses and data are transferred between the designated bus master and the memory or another of the external devices via the nondedicated bus during the next cycle after a then active bus master relinquishes control. The priorities of the external devices can be changed dynamically.

Abstract: A computing system architecture includes a central processing unit having a channel, arithmetic and logic unit, a plurality of working registers, and control logic; a plurality of local storage registers; a main storage; an executable control store; one or more input/output devices; and a multiplexed cycle steal and interrupt request common poll bus.The storage and input/output devices communicate with and are controlled by the central processing unit over a looped, or unidirectional bus and control channel including a bus in, a bus out, an address and a six-bit code bus, and a plurality of control lines. Bus out is operated to address the executable control store and main storage, and to provide data to the input/output devices and the local storage registers. Bus in is shared by the input/output devices and all storage devices and registers for transferring data and control information to the central processing unit.

Abstract: A computing system architecture includes a central processing unit having a channel, arithmetic and logic unit, a plurality of working registers, and control logic; a plurality of local storage registers; a main storage; an executable control store; one or more input/output devices; and a multiplexed cycle steal and interrupt request common poll bus.The storage and input/output devices communicate with and are controlled by the central processing unit over a looped, or unidirectional bus and control channel including a bus in, a bus out, an address and control bus, and a plurality of control lines. Bus out is operated to address the executable control store and main storage, and to provide data to the input/output devices and the local storage registers. Bus in is shared by the input/output devices and all storage devices and registers for transferring data and control information to the central processing unit.

Abstract: A computing system architecture includes a central processing unit having a channel, arithmetic and logic unit, a plurality of working registers, and control logic; a plurality of local storage registers; a main storage; an executable control store; one or more input/output devices; and a multiplexed cycle steal and interrupt request common poll bus.The storage and input/output devices communicate with and are controlled by the central processing unit over a looped, or unidirectional bus and control channel including a bus in, a bus out, an address and control bus, and a plurality of control lines. Bus out is operated to address the executable control store and main storage, and to provide data to the input/output devices and the local storage registers. Bus in is shared by the input/output devices and all storage devices and registers for transferring data and control information to the central processing unit.