I had this issue as well, though on my Y510p. It only happened to me while I was on battery, which meant my power settings changed to operate in "unplugged" mode. It is indeed an issue with the "Lenovo Power Management" software. You can try uninstalling it, but I'd recommend playing around with the settings along with windows power options settings. Since I was able to get the choppiness to go away with changing settings, there might be need for concern if you try many setting combinations without improvement. For those of you who have uninstalled the software suite and are still having issues, I think it's because the "Lenovo ACPI-Compliant Virtual Power Controller" is still installed. Try going into device manager > System Devices and uninstalling it.