Timur wrote:Well, once you write about CPU load then you ask about DPC latencies. This is a bit confusing.
Same issue as this: http://www.rme-audio.de/forum/viewtopic.php?id=11120
It's not a DPC issue, it's a cycling CPU usage that alternates between ~20% and ~40% on a single core, in a very regular fashion. When audio is playing it switches between ~0% and ~100% at a much faster rate. Unplugging the unit and plugging it back into the port fixes the issue until the computer is restarted.
Resource Monitor says it's due to deferred procedure calls and/or interrupt service routines. LatencyMon suggests USBPORT.sys as the possible culprit, having the highest DPC and ISR counts of any driver. Again it's not a DPC issue per se, since there are no spikes above 100 microseconds and my overall latency stays below 200.
I've done some research and it seems like USB audio devices in general cause this issue in certain cases. A hotfix was produced by Microsoft but it was apparently included in SP1, which I already have. I'm guessing the problem here is with the Microsoft USB driver, or with the way the Babyface communicates with it (firmware/driver issue). You guys would know better than me obviously but I'm just putting some thoughts out there to get the ball rolling.
Please consider possible ways to fix this that don't include: clean boots, reinstalling the USB controllers in the device manager, disabling power saving features, trying driver 0.966 or 0.979, switching USB ports, or disconnecting USB devices.