Dell UP2720Q 4K monitor with Macbook 16" M1 Max problems

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Dell UP2720Q 4K monitor with Macbook 16" M1 Max problems

I have two Dell UP2720Q 4K monitors daisy-chained and connected with a Thunderbolt 3 cable directly to the new MacBook 16" M1 Max laptop.

The MacBook does not recognize the native resolution of the monitor, which is 3840x2160. It sets the native resolution to FullHD1080. This results in oversized windows, system fonts, and icons. Setting a scaled resolution of 3840x2160 shows ridiculously small system fonts and icons, totally unusable.

On any of the scaled resolutions, the quality of fonts and other graphics looks substantially degraded. Fonts have a strange fuzzy halo around the edges (sometimes looks almost like a tiny dropped shadow).

These same monitors plugged in into the older Intel-based MacBook Pro 16 2019 work absolutely fine and do not have the same issues.

I searched the internet but can't find any solution that would work.

Posted on Jan 17, 2022 5:56 PM

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Answer 1

Best reply

Grant Bennet-Alder

Level 10

127,939 points

Jan 18, 2022 9:37 AM in response to andri227

A genuine ThunderBolt-3 cable, with the ThunderBolt symbol printed on the connectors at each end of the cable, measuring 1/2 meter long, is likely to be a 40Gbit/sec cable, and should be able to support a 4K display properly.

A cable longer than that is unlikely to be able to support a 4K display properly, because it does not have enough bandwidth -- unless you bought it as an ACTIVE genuine ThunderBolt 40Gbits/sec cable (and likely paid over US$60, just for the cable).

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Answer 2

Jan 17, 2022 6:32 PM in response to andri227

That's a 4K genuine Thunderbolt Display. It USB-C shaped port requires a Thunderbolt cable.

Input Connectors

1 x DP 1.4 (HDCP 2.2)
2 x HDMI 2.0 (HDCP 2.2)
1 x Thunderbolt(TM) 3 Upstream port (DP1.4)
1 x Thunderbolt(TM) 3 Downstream port (DP1.4)

so the cables you are using... what are they? do they have a ThunderBolt symbol at each end?

how long are they {half-a meter, two meters}

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Answer 3

Jan 17, 2022 6:34 PM in response to andri227

Displays Preferences shows SCALED resolutions. These are NOT the Hardware resolutions you display is set to. These are effective resolutions for TEXT when displayed on that display when you select Scaled.

They are intended to be a convenience for you, but they often cause concern and outright alarm instead.

To see the ACTUAL resolution your display is set to use:

 Menu > about this Mac > (system report) > Graphics & Displays

Select your display and scroll around until you see two items.

The first is self explanatory: 'Resolution:' 2560 by 1080

This is the hardware resolution at which your display is operating. Graphics are drawn at this Actual Resolution. But there is a problem -- If text were displayed at the Actual Resolution, it would be microscopic and unreadable.

The second resolution shown is 'User Interface Looks like:' this reveals the apparent size of text displayed on your display after scaling is applied ONLY to textual items.

Text is rendered at full resolution, then SCALED by the display Hardware by a factor (like 1.2 or 1.5, or 2.0) before it is aded to the display buffer. This makes it fully readable, yet maintains crisp edges that would be lost otherwise.

¿what settings are shown there?

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Answer 4

andri227 Author

Level 1

5 points

Jan 18, 2022 8:50 AM in response to Grant Bennet-Alder

See below the output

Apple M1 Max:

  Chipset Model:	Apple M1 Max
  Type:	GPU
  Bus:	Built-In
  Total Number of Cores:	32
  Vendor:	Apple (0x106b)
  Metal Family:	Supported, Metal GPUFamily Apple 7
  Displays:
DELL UP2720Q:
  Resolution:	6720 x 3780
  UI Looks like:	3360 x 1890 @ 60.00Hz
  Main Display:	Yes
  Mirror:	Off
  Online:	Yes
  Rotation:	Supported
  Automatically Adjust Brightness:	Yes
DELL UP2720Q:
  Resolution:	6720 x 3780
  UI Looks like:	3360 x 1890 @ 60.00Hz
  Mirror:	Off
  Online:	Yes
  Rotation:	Supported
  Automatically Adjust Brightness:	Yes

Both cables are TB3 (0.5, 1m).

Another frequent symptom I noticed is when changing scaled resolution I sometimes see the following popup

Preferences Error

There was an error in Displays preferences

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Answer 5

Jan 18, 2022 9:04 AM in response to andri227

<< Both cables are TB3 (0.5, 1m). >>

That was a multiple choice question. Cables that are about 1/2 meter long are COMPLETLY different from cables that are longer.

¿ How long are you cables?

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Answer 6

andri227 Author

Level 1

5 points

Jan 18, 2022 9:54 AM in response to Grant Bennet-Alder

Thanks, I will double-check the cables once again, maybe because the new MBP uses TB4 it does make a difference... However, I am still a bit confused why the exact same setup works perfectly fine on the Intel-based MacBook pro. It does not sound like it's a hardware problem.

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Answer 7

Jan 18, 2022 10:15 AM in response to andri227

Apple has pulled many of the display functions AND ThunderBolt functions into its own devices and software, mostly walking away from standard Intel Alpine-Ridge ThunderBolt controllers.

I think that is why the Actual Resolutions shown are so wonky (i.e., a 4K display that is showing at an impossible 6K resolution).

But the requirement for high-speed ThunderBolt cables has not diminished. 4K and higher demands a LOT of bandwidth, and different standards do not diminish those cable requirement in the slightest.

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