It would have to do with the video card driver. My card is OpenCL 1.1 but it can only be checked in the 64 bit version of Photoshop and not the 32 bit version. You can see if you have the latest video drivers by checking with Nvidia's website.
Before continuing,please have a look at the GPU FAQ
If the OpenCL checkbox is dimmed,it means Adobe GPU sniffer found a problem with the driver and disabled opencl. In that case you will have to wait for a new release. Are you sure your work in Photoshop depends on this? If not,you can wait for the next release.
You can also try NVDIA beta drivers. Here's what it looks like on the NVDIA's english site. Maybe the Chinese site has the same.
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