Research On Dynamic Frequency Scaling For SOC With Bus Load Monitoring

DFS (Dynamic Frequency Scaling) is a kind of real-time frequency scaling technique based on the technology of digital integrated circuits design. Compared to the DVS (Dynamic Voltage Scaling), its risk of design is not high and it is applied widely in SOC’s low power design. SOC(system on chip) is usually composed of a CPU core and several masters. It is observed that CPU core and masters’s working loads vary in different timeslots, so their needs of running frequencies also vary differently in different timeslots.The research of this paper has found that the tasks of the system have the property of regularity and locality. Each master’s demand of working frequency will vary depending on the regularity of running program. This paper aims to dynamically predict next period’s optimal CPU frequency and bus frequency according to the multiple history time slices of monitored working load information.Thus we can control the whole system running at the optimal frequency point. Thus the purpose of low power design can be realized. The innovation of this dissertation is showed below:1. DFS of CPU frequency based on CPU’s working load. This dissertation proposes two CPU frequency DFS methods:The first one is a kind of estimating method with the constraints of SOC’s whole performance demand and the frequency of system bus.The optimal CPU frequency can be caculated correspondingly.The second one is a kind of predicting method according to the regularity of CPU’s working load. The DFS system monitors the CPU working load periodly,and the DFS module can predict the next period’s working load according to the history working load information.Thus the optimal CPU frequency can be configured according to the CPU working load. The experimental results show that the configured CPU frequency varies along with CPU working needs and the predicting accuracy is higher than 69.9%.2. DFS of system bus frequency based on the masters’ working load.This dissertation proposes a kind of bus frequency scaling system. It monitors the masters’ working load status in every monitoring period. According to the monitored information and the performance needs, it predicts the optimal bus frequency in next monitoring period. And then it drives the clock management module to configure the optimal bus frequency correspondingly. Thus it can achieve the purpose of low power design when meeting the performance needs. The experimental results show that this dynamic power management strategy reduces the bus power consumption by 45.6%～-50.7% compared to the original static methods.The experimental results show that the dynamic frequency control system based on load monitoring system has a certain practical value.