CODi 3440x1440 Monitor with USB-C won't go beyond 2560x1440

[JohnEeeDee]

We have a CODi Ultrawide monitor that has the capability of 3440x1440 resolution, but when we have it hooked up to USB-C on a MacBook Pro 16" with M4 Pro, macOS shows 2560x1440 as the highest available resolution.

We installed BetterDisplay and tried to get macOS to show the 3440x1440 resolution, but after adding that resolution, we get the dreaded "Currently not available" message in BetterDisplay. We did try both Applying and Restarting (which most of the discussions that came up when I searched for "Currently not available" recommended), but still have the same issue.

The very strange thing is...it works fine at 3440x1440 when connected via HDMI rather than USB-C, with or without BetterDisplay. And perhaps more to the point, SwitchResX immediately and easily drives the monitor at 3440x1440 with no problem via USB-C, just by adding the custom resolution.

We want to use USB-C for the one-cable elegance of charging, display, peripherals, etc, and hooking up both USB-C and HDMI results in two monitors appearing in macOS that gets confusing when moving the mouse around. So we know the monitor and the Mac can drive the monitor at full resolution with SwitchResX or via HDMI, but BetterDisplay doesn't seem to be able to force it to the higher resolution when connected via USB-C. We even tried modifying the monitor specs manually in BetterDisplay to tell it the max resolution was 3440x1400, and it took effect because we changed the name of the monitor just to see if it was in effect, but still macOS only sees 2560x1440 as the max resolution.

We're using the cable that came with the monitor, and the M4 Pro USB-C/Thunderbolt ports do support full resollution, so we're at a loss as to why this isn't working via USB-C with BetterDisplay.

Of course, we could just use SwitchResX, but we thought this might be a good test case for BetterDisplay to add whatever capability SwitchResX has that it doesn't, at least in this particular scenario. Or we could be just missing some step or setting in BetterDisplay that's required to get this working.

Thanks for any hints!

[waydabber]

Hi @JohnEeeDee - when you add a custom resolution in BetterDisplay, it is a custom scaled resolution. Scaled resolutions will still output at the display's reported native resolution.

To add a custom timing, you need to use the app's EDID override feature. The app does not provide an UI to add a custom timing (or other low level EDID changes) as there are professional EDID editing apps that do this much better and expose all possible options. BetterDisplay can export the EDID in the right format for the free AW EDID Editor, you can open the EDID, fix the timing issue or any other problem and then apply the modified EDID with the app and configure it to be auto-applied when the display is connected. SwitchResX specifically has a feature to add custom timings and append it to the EDID - I assume this is what you did.

With all this said, it is very strange and extremely rare that the display does not expose the native resolution properly via USB-C - if this is the case, it is a fundamental issue with the display (it can be considered defective - maybe a firmware update can fix this)?

You can check (or switch) the low-level negotiated resolutions with this command (substitute DISPLAYNAME of course):

/Applications/BetterDisplay.app/Contents/MacOS/BetterDisplay get -n=DISPLAYNAME -connectionModeListAll

If you see 3440x1440 in the list, then the issue is not the lack of timing but the incorrectly reported native resolution (also an EDID issue). If this is the case, you can override the native resolution under Configuration Editing / More... / Edit native panel pixel resolution for the display, no EDID editing is needed.

If you attach the screenshot of what change you did in SwitchResX that work, I can probably decide what is wrong. In any case, SWX is a great app - if it works and fixes your issue easily, just use it. SWX and BD can work nicely together (provided you only use SWX for EDID and display override stuff and use other aspects of BD).