International Business Machines Corporation

Brice J Feal

Stamatis Vassiliadis

Michael Putrino

Gerald George Pechanek

Ann E Huffman

Eric M Schwarz

David James Shippy

Donald J Hanrahan

In a data bus system which links a plurality of users, user access to the bus is provided by an arbiter which responds to a plurality of user requests for bus access by employing an adjustable priority scheme for granting access. When a user has access to the bus, the arbiter updates user priority by assigning the lowest priority to the current user and upwardly adjusting the priorities of all currently-requesting users.

Least recently used arbiter with programmable high priority mode and

The invention determines when two operands are equivalent directly from the operand without the use of an adder. In one embodiment, conditions for the sum being equal to zero are determined from half sum to carry and transmit operators derived from the input operands. These operands are used in some known types of adders and, thus may be provided from a parallel adder to the condition prediction circuitry. In another embodiment, the equations for a carry-save-adder are modified to provide a circuit specifically designed for the determination of the condition when the sum of the operands is equal to zero. This sum is equal to zero circuit greatly reduces the gate delay and gate count thus allowing the central processing unit to determine the condition prior to the actual sum of two operands. This allows the CPU to react to the condition more quickly, thus increasing overall system speed.

Apparatus and method for prediction of zero arithmetic/logic results

Method and apparatus for modified carry-save determination of

An apparatus for predicting parity of a result produced by selection of the most or least significant thirty-two bits produced by a thirty-four bit adder, the parity being predicted concurrently with and independently of the result. Parity for byte Si of the selected result is derived by circuitry implementing the relationship:

Parity prediction for binary adders with selection

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Endicott, NY, United States of America

Brice J Feal