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I will demonstrate my idea on a 4K monitor, there are 4 options:

  • Native 4K
  • 1692p
  • 1440p
  • 1080p

From What I undersrand, the 4K and 1080p should be on par when it comes to the GPU demands as the 1080p is derived (directly scaled, i.e., zoomed) from 2160p. However, 1440p and 1692p, respectively, are more demanding as macOS has to scale down from 2 times higher resolutions, i.e., 2880p and 3384p.

If it works that way, then by the same logic, if I list the GPU demands with the 2K and 5K monitors, then the scale would be as follows (starting from the least GPU heavy case):

  1. (2K) 1440p native, (2K) 720p
  2. (4K) native, (4K) 1080p, (2K) 1080p
  3. (2K) 1152p
  4. (4K) 1440p, (5K) native, (5K) 1440p
  5. (4K) 1692p
  6. ...
  7. ...

Does it work that way or am I getting it all wrong?

I have been wondering about this for a long time as Windows uses a different mechanism, which is clear to understand.

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It is not clear to me how your ranking is supposed to function.

You need to make a distinction between whether or not you're using HiDPI-mode ("Retina-mode"). This is very important.

You can run a 4k monitor at 4k resolution (as seen by the monitor) in two modes - either HiDPI Retina or native 4k. The HiDPI mode is the default chosen by macOS. In this case it will be labelled as "Looks as 1080p".

When running in "native 4k" everything is rendered 1:1. This means that user interface elements would typically look very small on a normal sized monitor.

When running in "HiDPI" mode, you'll see that it will be labelled "Looks like 1080p". I.e. text and user interface elements are the same physical size on the monitor as had you chosen a native 1080p resolution. However, text, video, pictures, etc. are actually rendered at 4k (3840x2160) resolution, giving you crisper text and full resolution video.

Whether or not "native 4k" mode or "HiDPI mode" is more taxing on the GPU depends on what applications you're running. If you're looking at a blank desktop, the "native 4k" mode should use the fewest resources on the system as a whole.

If you choose a different resolution, like for example 1440p in HiDPI mode, the system will actually render at double the size - i.e. 5120x2880 - and then scale it down to the 4k output for the monitor. In this case the system has to perform more work than it did for the "Looks as 1080p" HiDPI mode.

However, if you run 1440p in native mode, i.e. the output signal for the monitor is 1440p - then that is usually less taxing for the system than 4k native.

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  • I see, thanks a lot for the explanation! So, I was just partially correct. Just to be 100 % certain, running, e.g., 1152p on a 2K means scaling down from a theoretical res. 2304p, hence a slightly more demanding than 4K native / 1080p in HiDPI? I know what my other confusion was (and still a bit is, but not performance-wise). The 4K monitor automatically connects with HiDPI mode while the 2K does not. Is there any way to use 2K monitor in HiDPI mode (or there are not enough pixels)? – Josh E. Jan 25 at 17:02

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