16 Multi - Core CPU Air Cooling

High speed electronic devices generate more heat than other devices. This chapter is addressing the portable electronic device air cooling problem. The air cooling limitations is affecting the portable electronic devices. The Multi-Core CPUs will dominate the Mobile handsets Platforms in the coming few years. Advanced control techniques offer solutions for the central processing unit (CPU) dynamic thermal management (DTM). This chapter objective is to minimize air cooling limitation effect and ensure stable CPU utilization using fuzzy logic control. The proposed solution of the air cooling limitation focuses on the design of a DTM controller based on fuzzy logic control. This approach reduces the problem design time as it is independent of the CPU chip and its cooling system transfer functions. On-chip thermal analysis calculates and reports thermal gradients or variations in operating temperature across a design. This analysis is increasingly important for the advanced digital integrated circuits (ICs). At today’s 65nm and 45nm technologies, adding cores to CPU chip increases its power density and leads to thermal throttling. Advanced control techniques give a solution to the CPU thermal throttling problem. Towards this objective, a thermal model similar to a real IBM CPU chip containing 8 cores is built. This thermal model is integrated to a semiconductor thermal simulator. The open loop response of the CPU chip is extracted. This CPU chip thermal profile illustrates the CPU thermal throttling. The proposed DTM controller design is based on 3D fuzzy logic. There are many cores within CPU chip, each of them is a heat source. The correlation between these cores temperatures and their operating frequencies improves the DTM response and reduce the air cooling limitation effect. The 3D fuzzy controller takes into consideration these correlations. This chapter presents a new DTM technique called “Thermal Spare Core” algorithm (TSC). Thermal Spare Core (TSC) is a completely new DTM algorithm. The thermal spare cores (TSC) is based on the reservation of cores during low CPU utilization and activate them during thermal crises. The reservation of some cores as (TSC) doesn’t impact CPU over all utilization. These cores are not activated simultaneously due to the air cooling limitations. The semiconductor technology permits more cores to be added to CPU chip. That means there is no chip area wasting in case of TSC. The TSC is a solution of the Multi-Core CPU air cooling limitations.