It sound like control rate things might be in better shape on the H9000. Can you comment on what sort of scheduler is running the control stuff?
Well, the control code is run at a lower priority than the audio processing. So, you can't rely on the control loop to execute with any particular frequency as it depends on how busy the DSP is doing real-time audio processing. As the DSPs have four cores, the OS can spread the control processing across all of them, so if you have one or two algorithms that are very DSP intensive, they probably won't affect the control code too much, since it will just be scheduled on the cores that are less busy.