While trying to validate the installation of tensorflow-gpu, I get an ImportError when trying to execute \"import tensorflow as tf\". I am using a Quadro K620 on Windows 7.
I am a chinese, so my english is poor, and my answer is that however you use cudnn 7 or 6 or 5 , you must rename the dll from cudnn64_x.dll to cudnn64_6.dll after you copy files.
maybe soon, you need to rename the dll to 7 or 8 or 9 as possible.