Using a Local Prefetch Strategy to Obtain Temporal Time Predictability

Today´s embedded systems are considering cache as inherent part of their design. Unfortunately, cache memory behavior heavily depends on the past references which model a large execution history and makes WCET analysis impractical. This paper presents a novel prefetch memory mechanism that simplifies the prediction of cache hits/misses because the memory access times are independent of the execution history. We use local prefetching into on-chip memory together with a custom-designed prefetch controller instead of cache memories to provide for time-predictable memory accesses. To be competitive in code execution time, our approach relies on a special organization of main memory and on a modified compiler that generates code layouts to allow for parallel prefetching from different memory banks. The proposed solution is still in a conceptual phase. The paper discusses design decisions and parameters to be explored.