While PC trace is on, and the trace is in predication or general event profiling mode, trace hardware captures events in each cycle. Trace hardware inserts this information into data logs, and does a right shift to compact the data. The trace window will eventually close, either because tracing has been turned off, or because a periodic sync point is generated to reset the window. In either of these two cases, the data log may be incomplete, fully packed, or just overflow into the next packet. An index is generated pointing to the last valid location in the data log in order to save transmission bandwidth.