Time Predictable CPU and DMA Shared Memory Access

In this paper, we propose a first step towards a time predictable computer architecture for single-chip multiprocessing (CMP). CMP is the actual trend in server and desktop systems. CMP is even considered for embedded realtime systems, where worst-case execution time (WCET) estimates are of primary importance. We attack the problem of WCET analysis for several processing units accessing a shared resource (the main memory) by support from the hardware. In this paper, we combine a time predictable Java processor and a direct memory access (DMA) unit with a regular access pattern (VGA controller). We analyze and evaluate different arbitration schemes with respect to schedulability analysis and WCET analysis. We also implement the various combinations in an FPGA. An FPGA is the ideal platform to verify the different concepts and evaluate the results by running applications with industrial background in real hardware.