I see this all over the internet. People asking about the refresh rate on Apple’s new iMac 5k. Well if it was 30hz everyone would be disappointed. I tested it several ways. I always had to use software methods though. I am pretty sure I know the refresh rate.
First Refresh Rate Test on the iMac
2nd iMac 5k Refresh Rate test
I also ran several games at the 5K resolutions with V Sync enabled. This gave me a reading of 60hz. My conclusion is that the Retina iMac runs at 60hz. Some people disagree with me though. I don’t have anyway to test it with hardware. Everything I have done on the new iMac leads me to a 60hz monitor. If it was 30z it would be very noticeable.
I have also loaded bootcamp on it now and in Windows 10 it shows 60hz.