How to use "unsupported" 2560x1440 mode of Dell monitor without 3rd-party software?

Tech Support
1

Unfortunately macOS does not support the native 2560x1440 resolution of my Dell U2711 monitor (it uses ugly scaled 1920x1200 instead). On my personal MacBook Air M1 I work around this using SwitchResX. However, I temporarily need to (also) work on a MacBook Pro M3 from work with the same monitor and I am not allowed to install any 3rd-party software on that machine.

How can I still use this “unsupported” 2560x1440 mode without 3rd-party software?

My hope was that I could just copy the DisplayProductID-a055 EDID override file that SwitchResX put in /Library/Displays/Contents/Resources/Overrides/DisplayVendorID-10ac between the machines, but that does not seem to work.

What might work?

2

Something feels very odd to me about this problem. I had a similar monitor (old Dell 27" @ 1440p) and my M1 Pro machine never had issues outputting to the native panel resolution without extra software. My first thought would be to check the cable being used. If it’s a USB-C to C cable, make sure it’s actually rated for the full speeds and not a charging cable with a 480 mbps data rate. I can’t test again unfortunately but that would be my first guess

3

My M1 MBP Pro is outputting to a Dell U2715 at 2560 x 1440 resolution on the Dell. No issues at all.

The MBP is connected to a dock which is connected to the monitor via DisplayPort.

I recall with my monitor when I upgraded to the M1 MBP, the advice at the time was that DisplayPort provided a more reliable connection than HDMI.

You might want to investigate whether your monitor has a DisplayPort output which you can then use with a DisplayPort to USBC cable.

4

The monitor is rather old (from 2010-ish?) and has no USB-C input. It does have DVI (2x), HDMI, DisplayPort and VGA inputs. Unfortunately the monitor limits HDMI to 1920x1080, because it runs in some kind of “TV mode” on that specific input.

I have two USB-C dongles that I can use and two different cables: HDMI (dongle) to DVI (monitor) and DisplayPort (dongle) to DVI (monitor). All combinations of dongles/cables can drive 2560x1440 with SwitchResX on my Air, but only 1920x1200 without it.

In the past (still an Intel Mac instead of Apple Silicon) I also used a USB-C to DVI cable (without a dongle), but that cable broke and also needed SwitchResX (or at least an EDID override) to run 2560x1440.

5

Oh, the dongle I got from work (one of the two mentioned above) also has a DVI output. I tried the dual-link DVI cable that I (successfully) use to drive 2560x1440 on my Windows PC and am again stuck with 1920x1200 on the Mac…

Somehow macOS is limiting what’s possible?

(And I think I used EDID overrides on Intel Macs to work around that, but this does not seem to work on Apple Silicon?)

6

On the very slight chance that you haven’t already done the thing in this video, I offer up the thing in this video: https://www.youtube.com/watch?v=w7N3PsMvDaI

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7

Yes, I already did that.

1920x1200 is the highest resolution in my list; 2560x1440 is not included (unless I run SwitchResX).

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