부산대학교 도서관

This paper proposes a runtime voltage-scaling method that optimizes the supply voltage (V dd ) and the threshold voltage (V th ) under a given delay constraint. This paper refers to the optimal voltage pair as a Minimum Energy Point (MEP). This paper firstly proposes a closed-form continuous function that determines the MEP over a wide operating performance region ranging from the above-threshold region down to the subthreshold region. The MEP dynamically fluctuates depending on the operating condition determined by a given delay constraint, an activity factor and a circuit temperature. In order to track the MEP, this paper proposes a voltage scaling technique enabling to set Vdd and V th to near the MEP without iteratively tuning the voltages based on the proposed function. Existing MEP tracking techniques iteratively tune V dd , which may not be suitable in terms of (1) the hardware design cost for generating a number of V dd S and (2) the MEP tracking time. Measurement results based on a 32-bit RISC processor fabricated in a 65-nm process technology shows that the proposed method estimates the MEP within a 5% energy error in comparison with the actual MEP operation.