The Problem
On my system if I move a window or change tracks etc. I would get, and hear, audio dropouts.
These dropouts were really annoying, especially when using looped sections while mixing.
After much research using the internet and Cubase forums I determined a solution for my system. It may help other users so I outline my solution here.
Logically with the power of my graphics card, 2GB of DDR3 GPU memory with fast bandwidth, I felt it had enough power to handle the display needs of Cubase.
As we now have to use the Aero Graphics System to run Cubase 8 the OS requires time to do its Aero thing. Even though we can optimize Aero for maximum performance and appearance I don’t think it can use the graphics processor (I may be wrong here)
Cubase, by default, sets its processor priority to “high” (See Windows Task Manager) which seems to be desirable for a DAW. However the Processor Affinity for Cubase is allocated to all CPU predecessors.
On my system I have 8 CPU processors. By changing the Processor Affinity to allow Cubase to only use CPUs 0 to 6 (Uncheck CPU 7) the asio dropout problem completely went away.
It seems that allowing the OS a bit more processing time to its thing really helped.
This solution
I created a short cut to always start Cubase with this affinity.
On Windows.
- Create a standard short copy on the desktop.
- Right click and select properties.
- In the Target: setting add C:\Windows\System32\cmd.exe /c start “Process Monitor” /affinity 7F before the current text.
e.g., C:\Windows\System32\cmd.exe /c start “Process Monitor” /affinity 7F “C:\Program Files\Steinberg\Cubase 8.5\Cubase8.5.exe” - Change the Run: setting from “Normal Window” to “Minimized”
Hope this helps 
My Test System
Audio
Behringer FCA1616
Streaming buffer depth = 2000us
ASIO buffer depth = 10.0 ms 480 samples
Graphics card
NVIDIA Quadro K620
Operating System
Windows 7 Ultimate 64-bit SP1
Cubase 8.5