Latest on win 10 compatibility...
http://forum.renoise.com/...yinfo-thread/?p=331519

Sorry to keep banging on but heck... why not...
 
In mixcontrol I was on a buffer size of 128, and medium firewire driver latency before, and now I'm running as good if not better on 64 and short!
Wow!
The negative side of the coin shows that the drivers have been far from optimal until now. Glad it got spun around...
Focusrite did get a little bad "press" lately, the rumours going around were that their firewire interfaces are not the fastest, guess this is their answer to this question.

There may be a reason that MixControl 3.6 is only listed for the Saffire PRO 40. I had two instances where "no sound" occurred on my 24 DSP. The first I found the Windows sound card settings had been altered to another bit depth/sample rate (and set to exclusive mode) - these are also the default for when MixControl is installed, somehow it reverted. The second I couldn't find the cause (even setting the Saffire to Windows default had no sound from any program). Very freaky that second one... I ended up uninstalling 3.6 and put 3.4 back on this machine.

Contact Focusrite I suggest...