How can I get 1080p HiDPI at 60Hz on a 2160p screen?

I just noticed something on the monitor's specifications page.

It claims that the monitor supports vertical frequencies (i.e., refresh rates) of

• 24 Hz to 60 Hz - HDMI 1.4
• 30 Hz to 60 Hz - DisplayPort

Google search turns up several sites saying that HDMI 1.4 is incapable of supporting 4K resolution at 60 Hz. Most say the maximum refresh rate that HDMI 1.4 supports for 4K resolution is 30 Hz.

If this monitor really has only a HDMI 1.4 port, that claim of 60 Hz for the HDMI input may be a typo.

It's looking to me more and more like what you want is a USB-C to DisplayPort connection.

Mac mini (2024) - Tech Specs - Apple Support

Connect a display to Mac mini - Apple Support

A M4 Pro Mac mini should support a refresh rate of up to 60 Hz on all of its displays, whether you connect them using USB-C, Thunderbolt, or HDMI. If you are willing to limit yourself to a total of two displays, the M4 Pro Mac Mini's HDMI port can drive a 4K display at up to 240 Hz.

Acer Store (Ireland) – Predator Gaming Monitor XB271HK

This appears to be the monitor in your screenshot – a 27" monitor with a resolution of 3840x2160 pixels, a 60 Hz refresh rate, and two video inputs: DisplayPort and HDMI.

I can't find any information on this display's color depth, or on the HDMI version it supports. My understanding is that HDMI v2.0 does not have enough bandwidth to support all of

• 4K resolution
• 60 Hz refresh rate
• 10-bit-per-channel color
• 4:4:4 RGB encoding (anything else is effectively a way of reducing resolution)

at the same time. Something has to give, and that something might be the refresh rate. So IF the monitor has the 10-bit-per-channel feature that might be the reason for the 30 Hz refresh rate.

If it is, then either

• Turning off 10-bit-per-channel color in the monitor's menus (if you have the option), or
• Using a USB-C to DisplayPort adapter cable instead of a HDMI to HDMI cable

might solve the problem.

One thing that does seem odd is that your resolution list shows both

• 1920 x 1080 (par défaut)
• 1920 x 1080 (HiDPI)

So is your Mac presenting two identical Retina/HiDPI choices, and no low-resolution one? That would seem odd. Or is it presenting 1920 x 1080 (low resolution) as the (default) even though it knows the display is a 3840 x 2160 one? That would also seem odd.

Could you do a little experiment?

What happens if you run System Information (Option- > System Information), select Graphics/Displays … then, for each of the two Displays Settings choices above,

• Make that choice
• Do a File > Refresh Information in System Information
• See how the Graphics/Displays information has changed in response to the new Displays Setting choice?

E.g., this is what I see if I pick "1920 x 1080 (Default)". The drawing canvas "Resolution" has twice as many pixels in each direction as the "UI looks like" (Displays Settings) resolution, which tells me that this is a Retina/HiDPI mode in which Retina-aware applications will draw letter shapes and fill in photo areas at a 3840x2160 level of detail.