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I have a Mac Pro 5,1* with an Nvidia Quadro K1200 graphics card. Note that while this card is not officially supported by Apple, it works perfectly with Nvidia's graphics driver. The K1200 powers two Dell P2415Q 4k monitors (4k@60Hz). I am very happy with the monitors, as the 4k is a massive improvement over the 1080p monitor I was using before.

However, my computer would beg to differ. For some reason, MacOS has decided not to recognize the screens as 4k. All of the System Preferences, System Report, and other display information insists the screens are 1080p60.

Photoshop recognizes the screens as 4k (for example, when a 24MP image opens full screen, the zoom is ~40% (on a 1080p screen, it would be ~15%). When I take a screenshot that is 2px wide and 4px tall (as recognized by the system), I can count 4px across, and 8px vertically.

More information: I am running MacOS Sierra 10.12.2 build 16C67. This discrepancy is on the "default" resolution scaling. I can choose other scaled resolutions, but only up to 3360x1890, which is significantly smaller than the official 3840x2160 the screen supports (which I appear to be getting).

My question: why does this discrepancy exist?

*Note: the computer is actually a 2009 model (4,1) but has the (5,1) firmware upgrade.

This is the output of system_profiler SPDisplaysDataType:

Graphics/Displays:

NVIDIA Quadro K1200:

  Chipset Model: NVIDIA Quadro K1200
  Type: GPU
  Bus: PCIe
  Slot: Slot-2
  PCIe Lane Width: x16
  VRAM (Total): 4095 MB
  Vendor: NVIDIA (0x10de)
  Device ID: 0x13bc
  Revision ID: 0x00a2
  ROM Revision: VBIOS 82.07.7f.00.14
  Metal: Supported
  Displays:
    DELL P2415Q:
      Resolution: 1920 x 1080 @ 60Hz (1080p)
      Pixel Depth: 32-Bit Color (ARGB8888)
      Display Serial Number:
      Main Display: Yes
      Mirror: Off
      Online: Yes
      Rotation: Supported
      Adapter Type: DisplayPort
      Automatically Adjust Brightness: No
      Television: Yes
    DELL P2415Q:
      Resolution: 1920 x 1080 @ 60Hz (1080p)
      Pixel Depth: 32-Bit Color (ARGB8888)
      Display Serial Number:
      Mirror: Off
      Online: Yes
      Rotation: Supported
      Adapter Type: DisplayPort
      Automatically Adjust Brightness: No
      Television: Yes
  • What happens if you create a new user account and log into that? Does macOS recognise the 4K option then? Also, can you clarify what version of macOS you're running? – Monomeeth Jan 18 '17 at 2:49
  • @Monomeeth I used the guest account (is that good enough?) and tried it there. MacOS still has no clue that's it's powering 4K screens. I'm running MacOS 10.12.2 (16C67) (edited question to reflect this). – NoahL Jan 18 '17 at 2:53
  • Yeah, I would still create a new user account and try it, just to be thorough. – Monomeeth Jan 18 '17 at 2:55
  • @Monomeeth Tried creating a new account. It still thinks it's 1080p. It's not a problem impeding my work, I just think it's odd. – NoahL Jan 18 '17 at 3:00
  • How are you connected? I'd check the cabling is high-enough spec. There are several flavours of HDMI & DisplayPort, for instance – Tetsujin Jan 18 '17 at 6:54

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