Why 5120x1440 Doesn't Work with Apple M1

5120 x 1440 is neither 4K, nor is it 6K. Every GPU has its best for display, and scaled resolutions, and the M1 GPU may simply not support that odd 5120 x 1440 resolution. Your best external resolution, presuming that your display supports it will be via a USB-C to DisplayPort 1.4 cable, or to a true 4K Display with good quality HDMI 2.0 or higher (e.g. Ultra-Speed HDMI 2.1 cables which are backward compatible with the HDMI 2.0 spec.

But the discrete Radeon GPU on that 16 inch 2019 MBP very likely supports far more resolution choices than Apple has provided in the 8-Core M1 GPU, when using the same cable. Nothing you can do about it, if it doesn't.

Yeah, I forgot to mention ScreenResX, as I don't use it. The font size will be microscopic, and not certain you can have that screen resolution and larger fonts in menus, etc.

When my M1 mini arrives, I will be testing it with a 40 - 43 inch TV as a Desktop, so ScreenResX may play a role there too.

What do you mean you can't scale? Is there no option or is it not working? Did you hold down the Opt key when you clicked on the Scale Resolution radio button to get the expanded list of resolutions to scale to?

I am awaiting delivery of a Mac Mini M1 and plan to connect it to a 5120x1440 ultrawide display as well. I hope I can make it work with a reasonably comfortable scale option. If not, I'll try doing a Picture-by-Picture setup with the HDMI and TB3 ports feeding the monitor and doing a side by side arrangement. It's not perfect but at least I'll be able to use the entire display as two monitors next to each other.

Actually, your picture by picture idea is not bad. I use a samsung g9 monitor with a windows gaming rig and wanted to use the M1 for work (citrix and office 365 web). 2 side by side on the G9 would actually probably be ok.

Great info, thanks for sharing. As for cables to try, I've heard some other folks get results with this combination from Cable Matters:

https://www.amazon.com/Cable-Matters-DisplayPort-Resolution-Support/dp/B08C9NPC2S

My 16" MBP works fine with my Samsung 46" UltraWide monitor at 5120x1440.

I do have ScreenResX installed.

This is my connection:

MBP -> 4k 60Hz TB3 cable (40Gbps) -> Caldigit Dock -> Display Port Cable -> Samsung Monitor

With that connection is there any suitable resolution I may be able to obtain with a Mac Mini M1 connected the same way?

I have the same Samsung C49RG9x display and the new base M1 MacBook Air.

Using this adapter - https://www.amazon.com/gp/product/B07F17ZHJY/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

I also had to set the monitor setting to FreeSync OFF, 60hz; but could only set the 5120x1440 resolution using SwitchResX.

One other note I have is that 120hz refresh rate was possible @ 3840x1080 with EasyRes.

5120x1440 @ 120hz is still not possible with the combinations I've tried.

As I noted above I am using high-speed Thunderbolt 3 cable which is quite expensive to run a connection from my 16" MBP to my 49" Samsung UltraWidescreen display.

Nobody is talking about results using this Thunderbolt 3 connection with the new M1 mini so I am hoping that when I finally get my Mini in December I will have no display issues.

NJ Ron, I assume you mean you are using a USB-C to DisplayPort 1.4 cable that is plugged into a Thunderbolt 3/USB C port on your MBP 16” because the CRG90/G9 does not have a Thunderbolt 3 input?

If so, I have the same setup and my MBP works fine but my M1 is having tones of issues with DisplayPort (as many in this thread have stated). And HDMI on the M1 only seems to works up to 3840 x 1080 @100hz HDR.

I am not using a USB-C to display port cable. Using a High-Speed TB3 cable which is recommended for these monitors.

https://www.amazon.com/gp/product/B01N9J47EG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

16" MBP -> TB3 High Speed Cable -> Caldigit Dock -> DisplayPort Cable -> C49RG90 Monitor

There is a high-speed TB3 to Display Port cable made by Moshi that may work. I have not tested it, but others have recommended that this could be a solution

https://www.amazon.com/Moshi-USB-C-DisplayPort-Cable-1-5m/dp/B077S9DZGK/ref=sr_1_3?crid=2JTP95XSG9K43&dchild=1&keywords=moshi+usb-c+to+displayport+cable&qid=1606113487&s=electronics&sprefix=Moshi+%2Celectronics%2C151&sr=1-3

So, I need to find someone using higher-speed USB-C TB3 cable to Display Port definitively saying that this will not work with the M1.

I take it you tried, in display settings, to click the scaled option while holding the option key on the keyboard?

Were you able to push the monitor to 5120x1440 @60Hz using SwitchResX or similar display adjustment app?

Someone on Reddit with an M1 MacBook Air confirmed that they got it working with the CalDigit dock.

https://www.reddit.com/r/mac/comments/jvwju9/new_macbook_pro_m1_not_working_with_ultra_wide/gd1557a/

@NJ Ron, sorry, I forgot that you had already stated your connection configuration. The Caldigit dock is acting as a TB3 to DP converter. I believe it is DP 1.2. I have seen other suggestions that setting your monitor DP level to 1.2 can help, although it made no difference to me. I have installed ScreenResX to help see what the CRG90 and M1 negotiate as possible resolutions/frequencies and to select some that the M1 does not present in Display properties.

I can confirm that I KNOW and have had the M1 Mac mini successfully display 5120 x 1440 @120hz SDR with my CRG90 using a USB-C to DispalyPort cable (2 different cables). But the M1 and CRG90 do not negotiate a connection properly or with consistently and for me usually presents with a blank screen, no backlight, no rear lighting.

The most consistent way I have had the CRG90 work with the M1 is to have another monitor hooked up to HDMI (or the CRG90 itself) and when it detects the CRG90 over DP as an extended desktop screen, increase the resolution on the HDMI monitor and then unplug the HDMI and the CRG90 remains as my primary screen until I reboot (it worked while waking from sleep). This approach/work around worked for me a number of times.

I can NOT say the two won't work. I can say it is buggy at best. It has worked flawlessly on HDMI at 3840x1080 @100hz HDR

I am having a new adaptor delivered that others have reported better success with and will try, again, the DP1.2 setting on the CRG90 to see if I can get better consistency.

Thanks for the update

I am still 4 weeks away from getting my Mini (though I suspect Apple will move that date up substantially) so you are going to be the pioneer here.

I am interested to see how the adapter you are purchasing works out.

Your results are going to assist the rest of us who don't know yet what to expect.

I did send some Feedback to Apple about this issue. They claim they read all Feedback sent to them so if they get enough inquiries on this subject perhaps they will tweak a future update of Big Sur to support these monitors.

Please, please, please report back when you get your adapter and let us know if it works out. Good luck and thanks!

Report back here and let us know.

Also, be sure you are aware of the extra options available in Mac display settings.

In display settings, click the scaled option while holding the option key on the keyboard. It brings up more options for you.