Look at this document. It should help you troubleshoot and it suggests settings to try out.
Photoshop CC and CC 2014 GPU FAQ
While the stock advice for Windows users is to go to the Intel site for updates, Mac users can only get their drivers in the Mac OSX system updates. So you need to be sure your OS is up to date. If you have an earlier version, like 10.7 or 10.8, it is possible an upgrade to 10.9 might help.