LAEC: Look-Ahead Error Correction Codes in Embedded Processors L1 Data Cache

As implementation technology shrinks, the presence of errors in cache memories is becoming an increasing issue in all computing domains. Critical systems, e.g. space and automotive, are specially exposed and susceptible to reliability issues. Furthermore, hardware designs in these systems are migrating to multilevel cache multicore systems, in which write-through first level data (DL1) caches have been shown to heavily harm average and guaranteed performance. While write-back DL1 caches solve this problem they come with their own challenges: they need Error Correction Codes (ECC) to tolerate soft errors, but implementing DL1 ECC in simple embedded micro-controllers requires either complex hardware to squash instructions consuming erroneous data, or delayed delivery of data to correct potential errors, which impacts performance even if such process is pipelined. In this paper we present a low-complexity hardware mechanism to anticipate data fetch and error correction in DL1 so that both (1) correct data is always delivered, but (2) avoiding additional delays in most of the cases. This achieves both high guaranteed performance and an effective solutions against errors.