Efficient trace data compression using statically selected dictionary

Abstract

Post-silicon validation and debug have gained importance in recent years to track down errors that have escaped the pre-silicon phase. Limited observability of internal signals during post-silicon debug necessitates the storage of signal states in real time. Trace buffers are used to store these states. To increase the debug observation window, it is essential to compress these trace signals, so that trace data over larger number of cycles can be stored in the trace buffer while keeping its size constant. In this paper, we propose several dictionary based compression techniques for trace data compression that takes account of the fact that the difference between golden and erroneous trace data is small. Therefore, the static dictionary selected based on golden trace data can provide notably better compression performance than the dynamic dictionaries selected in the current approaches. This will also significantly reduce the hardware overhead by reducing the dictionary size. Our experimental results demonstrate that our approach can provide up to 60% better compression compared to existing approaches, while reducing the architecture overhead by 84%.