Unfortunately, there were no further replies to that thread but I did see that my same question "pops up every once in a while". Anyway, my specific problem is I'm trying to QPSK demodulate + RS decode a 2MS/s, 1Mbps bit rate, 10GB IQ file. This works fine, but I'm getting a different number of successfully decoded packets every run. I am using a throttle block, and in fact tried to reduce the throttling rate to 200KHz (samplingrate/10), but it still doesn't seem to work. As for how much CPU my flowgraph is utilizing, it takes up around 80% of all 8 of my CPU cores at the regular sampling rate, while taking around 30% of my cores at samplingrate/10. Do you guys have any idea on what might be going on? The thread I'm referencing is from 2013, but is it still relevant? Any technical reasons for the non-deterministic behavior? I'm using 3.7.13.2.