Embedded instruction memory in automotive engine controllers

Embedded systems currently account for all but 2% of the microprocessor market. Yet often embedded processor cores are simply streamlined versions of microprocessors that were designed for desktop computers. In computer architecture research, the Standard Performance Evaluation Corporation (SPEC) benchmark programs are often used to evaluate the performance of computer systems. The characteristics of the SPEC programs do not match typical embedded applications , however, and therefore it is not clear to what extent performance studies conducted using the SPEC benchmarks are applicable to embedded systems. In this paper, the authors focus on a specific segment of the embedded market: automotive engine controllers. Using data gathered by tracing a state-of-the-art automotive controller, they present simulation results for a memory system that consists of a main memory containing compressed programs, a bus used to fetch compressed instruction blocks, a decompression subsystem, and an uncompressed instruction cache. They look at a number of system parameters, including the bus load, the average memory access time, and the performance ratio of the compressed versus uncompressed system. They also present an analysis of the static and dynamic (run-time) system behavior.