Temperature effects on on-chip energy measurements

Latest generations of microprocessors target to maximize energy efficiency over other constraints such as area or performance. This turn of events does not only affect the industry, the academia is also focusing it´s efforts in proposing new solutions to maximize energy efficiency of computations at all levels, from hardware to software. While voltage, frequency and activity factors are usually considered by researchers in their works, temperature is usually left aside in their calculations or models. In this work we present an evaluation of the effects of temperature in real hardware taking advantage of the relatively new hardware energy counters available since the second generation of Intel^® Core™ processors. Results show an average 5% energy increase with every 8-10 degrees Celsius increment. After certaint temperature (80-100C), the processor starts throttling it´s frequency to prevent permanent damage on the die. Based on these results we will discuss some “good practices” when evaluating power and energy based on on-chip energy measurements.