ubuntu16.04+1070ti+nvidia384 cuda8.0 not working

I have installed nvidia driver 384.111 through apt install nvidia-384. Previously I installed cuda9.1 with its 387 driver, but cannot get to GUI, thus I remove 9.1, rollback to 384 and install cuda8.0 via runfile. Then I manage to compile the samples, but deviceQuery return 35, unable to detect my 1070Ti. What’s the problem?

installing CUDA 8 via runfile is not recommended after installing a driver via apt

Follow the instructions in the linux install guide to clean out old installations. Then start over, get your installers here: [url]http://www.nvidia.com/getcuda[/url]

and read the linux install guide carefully here: [url]Installation Guide Linux :: CUDA Toolkit Documentation

you can find older toolkits by googling “cuda toolkit archive” and the appropriate install guide will be linked from the download page

Thank you for your advice.
Today I have removed driver nvidia-384 by apt, and then uninstall cuda by runfile. Then I reboot, press Ctrl+Alt+F1 and then install cuda again. This time I accept nvidia-375, but no opengl files because I remember it will cause to loop login. And I update-initramfs -u, then reboot. But then the GUI becomes very low definition, thus it’s not correctly displayed well on my 2K screen. Although lspci | grep -i nvidia shows my GPU, but then ls /dev | grep nvidia does not show any thing. How can I fix this?
I have tried install nvidia-384 by runfile directly, but failed. The log file says pre-script failed, and then failed to build kernel module. It’s a implicit function declaration, so I guess maybe dependency error.