I bought a 980 Pro yesterday. I also have a 970 where my OS is installed. Today I was trying to copy a large file from the 970 to the 980 and experienced a very strange intermittent slowdown. Most of the time I am copying data to the 980 at 9MB/s with occasional massive jumps in speed to 2GB/s for less than a second.
Note that copying from the 980 to the 970 is very fast. The file (7GB) shown in the below video copies from the 980 to the 970 in 2 or so seconds.
Here is the video showing what is happening. Any ideas or suggestions to help me fix this? All drivers are up to date, firmware, magician all up to date, etc. etc..