Understanding System Level Caching Behavior in Multimedia SoC

A typical multimedia SoC consists of all or a subset of hardware components for image capture & processing, video compression and de-compression, computer vision, graphics and display processing. Each of these components access and compete for the limited bandwidth available in the shared external memory. Meeting latency (e.g., display) and throughput (e.g., video encode) is a critical problem to solve for such SoCs. In typical SoCs, this problem is solved using system level caches. However in this paper, we show results that indicate system level caches are not beneficial for multi-media traffic both in terms of DDR bandwidth savings as well as for latency reduction. We also show results of desirable features to improve multimedia performance in SoCs using a system cache.