The DisplayPort hooked up to my desktop performs beautifully at 4k at 60 hz and my MacBook hooked up with Apple's multi port adapter works well at 4k 30 hz on the other HDMI port

60 Hz, when you read the system requirements inside the manual it says that only the Nvidia graphics card supports the 60 Hz, all others, including Xbox One S which uses a version of AMD, will only display at 30 Hz.