International Business Machines Corporation

Maarten Boersma

Harry S Barowski

Tim Niggemeier

Gunnar Spiess

A method of power gating a microprocessor having an instruction scheduling unit for receiving issued instructions from an instruction decoder; an execution unit receiving and sending signals from and to the instruction scheduling unit; and a state machine. The method comprises: obtaining a number of instructions per cycle being issued to the instruction scheduling unit; determining, if the number of instruction per cycle being issued to the instruction scheduling unit is less than a threshold level, and then determining if at least two of the instructions being issued to the instruction scheduling unit are independent of each other only when the instructions per cycle is less than the threshold level; determining when at least two of the instructions being issued to the instruction scheduling unit are independent of each other; and power gating the microprocessor to gate off power to idle macros with a signal from the state machine.

Power down of execution units for issued instruction accumulation when issue rate of instructions falls below threshold and at least two are independent

A method of power gating a microprocessor having an instruction scheduling unit for receiving issued instructions from an instruction decode unit; an execution unit coupled to receive and send signals from and to the instruction scheduling unit; and a state machine located within the execution unit, the method comprises: obtaining a number of instructions per cycle being issued to the instruction scheduling unit; determining, subsequent to obtaining the number of instructions per cycle, if the number of instruction per cycle being issued to the instruction scheduling unit is less than a threshold level, and then determining if at least two of the instructions being issued to the instruction scheduling unit are independent of each other only when the instructions per cycle is less than the threshold level; determining when at least two of the instructions being issued to the instruction scheduling unit are independent of each other; and power gating the microprocessor to gate off power to idle macros with a signal from the state machine when the instructions are independent of each other without incurring significant loss of performance until an issue queue in the instruction scheduling unit is filled with instruction data.

Power gating processor execution units when number of instructions issued per cycle falls below threshold and are independent until instruction queue is full

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Holzgerlingen, Netherlands

Maarten Boersma