Thermal-aware scratchpad memory design and allocation

Scratchpad memories (SPMs) have become a promising on-chip storage solution for embedded systems from an energy, performance and predictability perspective. The thermal behavior of these types of memories has not been considered in detail. This thermal behavior plays an important role in the reliability of silicon devices and in their static (leakage) power consumption. In this paper, we propose two different techniques to improve the thermal behavior of SPMs. First, we propose a hardware-based, thermal-aware address translation technique that physically distributes memory accesses to consecutive addresses evenly over the whole memory area. Second, we propose a software-based, thermal-aware address generation technique. This technique tries to distribute the variables that are allocated to the SPM in such a way that an even thermal distribution is achieved. The first technique works particularly well for applications with a regular access pattern, whereas the second technique can also improve the behavior of applications with irregular access patterns. The two techniques thus complement each other and work well together. Using the first technique we show that the peak temperature of an SPM in 65nm technology, when running a typical streaming application, is decreased by up-to 10.0°C. Temperature cycling is reduced from up-to 14.8°C to almost zero in comparison with a non-thermal-aware solution. For our benchmark applications with an irregular access pattern, the second technique is able to reduce the peak temperature by up-to 3.5°C. These savings for both techniques are obtained without any performance degradation or extra silicon area.