Audio Latency / Drop-outs induced by MIDI interface (Report/Question)

In the last couple of weeks I discovered a degradation of my rig's latency. Even at 128 samples buffer with additional safety buffer (it is a Focusrite interface which has three modes: Recording, Balanced, and Mixing) I got drop outs at nearly no load at all.
First I thought it is a driver or some additional software - stuff like that. I tweaked around for a week, then I did a complete Roll-back of my machine with no result.
Ok, it seemed not to be a software issue. I invested another evening figuring out, what I changed at the hardware setup in the last weeks. The only thing was, that I connected a synth via USB-MIDI. In the past, it was connected via the MPC-MIDI Out port - essentially just another USB-MIDI (from the computer's perspective). So there should be no difference in audio performance of an extra audio interface...
I switched back to the old connection and voila: No Drop-outs anymore!
 
Conclusion: So, if you have to deal with strange latency issues, sometimes it is not your audio interface.
Question: Anybody made experiences like that? Or even better: Knows, what the root such problems could be?
 
 
 
 
 
 

scook
Dropouts happen when the DAW is data starved. This seems more like a DPC latency issue. It might be useful to run latencymon to check DPC latency (this is not the same as audio latency) in the configuration generating dropouts.

The last weeks I was looking into the topic of DPC. After checking the DPC with some tools, I figured out, that there is a storage problem. I was a little bit confused, because I use a high-end SSD. It seems that the DVD is one of the reasons. After disabling DMA the DPC latency was dropped by 80%.
 
Thank you!