TAB-BackSpace: Unlimited-length trace buffers with zero additional on-chip overhead

This paper presents TAB-BackSpace, our novel scheme to provide the effect of an unlimited-length trace buffer with no on-chip overhead beyond the existing debug logic. We present the theoretical foundation of our work, simulation studies on how we reduce the possibility of computing an erroneous trace, and results from the bring-up lab on real silicon of an IBM POWER7 processor, where TAB-BackSpace computes almost a thousand additional cycles of trace buffer information without any additional on-chip overhead.