Mac mini not offering higher resolutions than 1080p

[effbee]

Hello,

I want to connect a 4k Monitor (up to 3840x2160 pixels) to a late-2012 Mac mini. I tried two different Monitors, both via a Mini-Displayport to Displayport cable (no adapters).
System prefs has set the dimension to 1920x1080p. I tried also several tools like DisplayMenu or DisplayMaestro with monitor detection, but 1080p is still the highest resolution offered. The specs say, 2560x1600 should be feasible via Displayport.

Any hint what goes wrong?

Thanks, Frank

 

[pldelisle]

Video Support​

Support for up to two displays at 2560 by 1600 pixels, both at millions of colors
Thunderbolt digital video output

• Native Mini DisplayPort output
• DVI output using Mini DisplayPort to DVI Adapter (sold separately)
• VGA output using Mini DisplayPort to VGA Adapter (sold separately)
• Dual-link DVI output using Mini DisplayPort to Dual-Link DVI Adapter (sold separately)

HDMI video output

• Support for 1080p resolution at up to 60Hz

DVI output using HDMI to DVI Adapter (sold separately)

So your mac supports two QHD displays via daisy chained Thunderbolt, or one in the Thunderbolt as mini-DP. HDMI is maxed at 1080p.
If you try on your keyboard the ALT key while clicking on the Display settings in System Preference, does it show more available resolutions ?

 

[effbee]

The ALT key reveals a 'detect monitors' button. Pressing this has no visible effects, the list of resolutions still looks like this:
1600 x 900
1080p
1080i
720p

 

[BrianBaughn]

I get more resolution options when I click the "Scaled" button while holding down the Option key.

 

[effbee]

Yes, "scaled" is selected.
Pressing alt shows indeed more options, but all are lower - 640x480, 800x600 and alike. Seems like a filter that presents only the highest dimensions...

 

[joevt]

Yes, "scaled" is selected.
Pressing alt shows indeed more options, but all are lower - 640x480, 800x600 and alike. Seems like a filter that presents only the highest dimensions...

Is there a "Show low resolutions" mode button after pressing option and clicking "Scaled"?

 

[Fishrrman]

The 2012 Mini can't do 4k.

It CAN do 1440p, when connected to a NATIVE 1440p display.

My -guess- as to why you can't get 1440p on a 4k display:
In order to get 1440p on a 4k display, I believe the GPU has to first be able to connect and recognize the display "as 4k", and then "scale it down" to 1440p.

But (see above) the 2012 Mini can't do 4k, so it can't take these steps in the required order.

My guess is if you want to continue using the 4k displays you have with the Mini, it will have to be 1080p.

If you want 1440p, get a 27" or 32" display that is "native 1440p" and IS NOT 4k...

 

[effbee]

Fishrrman: I agree that this seems to be the only logical explanation right now.

I installed a tool called "SwitchResX" which can fine-tune frequencies. With this, I manage to display 2560x1440 using the full screen area and 2560x1600 with black borders on both sides. So this tool can detect the monitor the system and other tools can't.
But honestly it does look unclean/unsharp. I will continue to try tweaking...