While you can set the clockspeeds higher than 330MHz in Windows without causing issues, the problem is you can't boot with these settings and have to revert to the default settings each time you shut down or reboot Windows.
A user of a custom-design GTX 1070 notes that if the refresh rate of their monitor is set higher than 81 Hz (the highest refresh rate you can achieve with pixel clock staying under 330 MHz, the machine doesn't correctly boot into Windows. The splash screen is replaced with flash color screens, and nothing beyond. The system BIOS screen appears correctly (because it runs at low resolutions).NVIDIA hasn't acknowledged the issue yet but presumably they'll roll out a fix asap.
Via: TechPowerUp