Abstract: A microprocessor is configured for unchained and chained modes of split execution of a fused compound arithmetic operation. In both modes of split execution, a first execution unit executes only a first part of the fused compound arithmetic operation and produces an intermediate result thereof, and a second instruction execution unit receives the intermediate result and executes a second part of the fused compound arithmetic operation to produce a final result. In the unchained mode, execution is accomplished by dispatching separate split-execution microinstructions to the first and second instruction execution units. In the chained mode, execution is accomplished by dispatching a single split-execution microinstruction to the first instruction execution unit and sending a chaining control signal or signal group to the second execution unit, causing it to execute its part of the fused arithmetic operation without needing an instruction.

Abstract: An arbiter that performs accelerated arbitration by approximating relative ages including a memory, blur logic, and grant logic. Multiple entries arbitrate for one or more resources. The memory stores age values each providing a relative age between each pair of entries, and further stores blurred age values. The entries are divided into subsets in which each entry belongs to only one subset. The blur logic determines each blurred age value to indicate a relative age between an entry of a first subset and an entry of a different subset for each pair of subsets. The grant logic grants access by an entry to a resource based on relative age using corresponding age values when comparing relative age between entries within a common subset, and using corresponding blurred age values when comparing relative age between entries in different subsets. Each blurred age value represents multiple age values to simplify arbitration.

Abstract: A microprocessor is configured for unchained and chained modes of split execution of a fused compound arithmetic operation. In both modes of split execution, a first execution unit executes only a first part of the fused compound arithmetic operation and produces an intermediate result thereof, and a second instruction execution unit receives the intermediate result and executes a second part of the fused compound arithmetic operation to produce a final result. In the unchained mode, execution is accomplished by dispatching separate split-execution microinstructions to the first and second instruction execution units. In the chained mode, execution is accomplished by dispatching a single split-execution microinstruction to the first instruction execution unit and sending a chaining control signal or signal group to the second execution unit, causing it to execute its part of the fused arithmetic operation without needing an instruction.

Abstract: An arbiter that performs accelerated arbitration by approximating relative ages including a memory, blur logic, and grant logic. Multiple entries arbitrate for one or more resources. The memory stores age values each providing a relative age between each pair of entries, and further stores blurred age values. The entries are divided into subsets in which each entry belongs to only one subset. The blur logic determines each blurred age value to indicate a relative age between an entry of a first subset and an entry of a different subset for each pair of subsets. The grant logic grants access by an entry to a resource based on relative age using corresponding age values when comparing relative age between entries within a common subset, and using corresponding blurred age values when comparing relative age between entries in different subsets. Each blurred age value represents multiple age values to simplify arbitration.