Is it okay to use desktop or gui interface while using cuda?

I am trying to use CUDA with GTX 570. I am using Ubuntu 14.04 and CUDA has been installed successfully.

I think I should use desktop or gui interface with on-board VGA and run GTX 570 solely for CUDA, but seems not working well. (I set up on-board VGA as default in BIOS, but after installing CUDA, Ubuntu only provide gui in GTX 570 port.)

So, is it okay to use GTX 570 for both gui and CUDA? What is the standard way to use it?

If your on-board VGA is still active at boot time, and only goes dark when Ubuntu loads, then it should be possible via a rearrangement of your xorg.conf file, to get Ubuntu to use the on-board VGA for display also. In this case, you would remove all reference to the GTX570 from your xorg.conf, and this is the best approach.

You can use the GTX570 for both display and CUDA.

There will be two areas of limitation:

1. Interactivity - when running CUDA apps, your display will be unresponsive. For learning purposes, most CUDA kernels run for significantly less than 1 second, so this is not likely to be much of an issue for you (the display will freeze while the CUDA kernel is running). But if you want to run longer CUDA kernels, your system will be unresponsive during that time, and you may even run into Linux watchdog timeout issues. This document may also be interesting reading for you.

2. Debugging - When there is no X-server that is using the GTX570, then it can be easily used for debugging. However, you will not be able to debug (e.g. set breakpoints in CUDA device code) your CUDA apps when the GUI/display is also running on the GTX570.