Samsung CRG90 49" monitor to my Mac mini 2020 M1

I struggled with this as well and haven't seen many success stories but got it working and thought I'd share my specs:

• 2018 Mac Mini w/ 3.6 GHz Quad-Core Intel Core i3
• macOS 11.1 Big Sur
• Samsung c49rg90
• IOGEAR USB-C -> DisplayPort 1.2 cable

That's it! After my upgrade to Big Sur, it did still want to default to 3840 x 1080 as "default for display" but switching to "scaled" mode in Systems Preferences reveals 5120 x 1440 as an option.

Pretty solid so far. I was worried about the 1.2 Display Port cable rather than 2.0, but it seems fine.

Using cable that came with the LG monitor (USB-C to USB-C). USB-C to DP cable was Alogic I think. It was OK but not great with occasional loss of picture.

BTW, original problem eventually returned after hours of testing (sleep, shutdown, restart etc.) - so blaming physical network connection was a furphy.

Same thing here @MSB1968, With USB-C to Displayport I FINALLY too got things to work on my M1 mini with the C49RG9. And like you say, only with DisplayPort v1.2. I ordered this cable from Amazon:

https://www.amazon.se/dp/B00VI3OKL8?ref_=pe_20773151_507143461_E_301_dt_1

Another update: I have been using my MM-M1 as my daily driver now for two weeks and everything is pretty stable. I have turned off the option to put the screen to sleep, as after that it won’t resync. Reboot resolves but so can this:

1. plug in hdmi, unplug DP
2. turn on SBS, plug in DP with DP as second side
3. once synced, unplug hdmi and turn off SBS
4. switch to DP, works every time

So this certainly isn’t ideal but it does demonstrate that this is a software problem related to handshaking at certain resolutions.

I can wait for that while enjoying the other benefits of a way snappier, smoother and more stable Bluetooth than my MBP16” and way less fan noise while using primarily office 365 full thick and thin client suite. Only thing missing is a good vm player.

CRG90 is having all sorts of issues.

HDMI for me will only work to 3840 x 1080 @100hz HDR.

USB C to DisplayPort I got to work once before I rebooted (5120 x 1440 @120hz SDR) between 3 different cables. I have a new adapter coming tomorrow that others have had success with.

on my 1080p monitor over HDMI I got pink square artifacts on my screen... haven’t solved that yet.

Very flakey!

Might sound like an obscure question, but do you have an ethernet cable connected to the RJ45 port? If so, are you using the USB-C port nearest to the ethernet connection to connect your monitor?

I have a different (4K) monitor with USB-C and DP connection, and I have been having some strange USB-C monitor behaviour with an ethernet cable connected.

Spent $$$ on a range of different USB-C to USB-C, and USB-C to DisplayPort cables, and tried different monitors. Getting random disconnects and loss of picture, screen failing to wake properly, screen not detected at boot, etc. Changing to different USB-C port looked promising so assumed I had a faulty port and was about to return to Apple store.

Still testing, and it might fail again in 5 minutes, but using WiFi only SEEMS to have improved the situation (next step is to try different network cable).

Any luck with the new cable? I've had to revert to HDMI which seems to be working OK but I'm only running 4K at 60Hz. Really hate HDMI as a monitor connection, especially when I paid extra for a USB-C monitor. I'd settle for DP but tried a range of different cheap and expensive USB to USB and USB to DP cables without any luck.

Sadly no. After countless hours with Apple support we were not able to establish the cause of the issues. Symptoms were obvious and they in the end let me return it. I hear some are having good success with Big Sur beta 11.2. I didn’t get to test. I found no change records that identified a similar issue.

Having the same issue also.

I've tested and made very sure the problem was with the Mac M1 Mini itself and not the USB-C to DP cable I'm using, nor the C49RG9 either. This test in MacOS Big Sur 11.1.

Here's the test setup I used to demonstrate that the problem is indeed with the Mac M1 Mini:

Toshiba Tecra laptop (Core i5 8th gen, borrowed from the office mind you...), and this USB-C to DP cable ->

https://www.amazon.ca/gp/product/B00VI3OKL8/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1

This little laptop doesn't have the slightest problem driving the C49RG9 at full 5120x1440 @ 120 Hz, albeit no HDR, simultaneously with its own LED LCD. I tried each of the C49RG9's DP inputs, both with the same beautiful results. Ok, so, the cable works as does the C49RG9. Back then to the M1 Mini.

With a single USB-C to DP connection alone, no amount of rebooting the M1 Mini will ever make an image appear on the C49RG9 (don't know if a signal is even being sent to the display or if the display and the Mini are just failing to negotiate?). But, BUT, with both the HDMI and USB-C to DP cables connected, rebooting the Mini yields two distinct displays in system preferences. Unfortunately, neither one of them can be set (scaled) to full resolution. Both remain limited to 3840x1080 at whichever frequency (60, 100, 120 Hz).

Then I tried something: with both cables still connected, I went ahead and disconnected the HDMI cable, leaving only the USB-C to DP cable connected. Lo and behold, I still had an image on the C49RG9!!! Oh, that's strange... Well, at least it proves the Mini's USB-C ports work, sort of (tried this stratagem with both ports), as does the cable, but something is definitely awry with the M1 hardware or drivers. Unfortunately again, even with only the USB-C to DP cable now connected, resolution still maxed out at 3840x1080, whichever frequency.

With these results in hand, I called Apple and opened a case file. Apparently it is a known problem but the advisor - actually the advisor's supervisor - couldn't confirm if a fix was in the pipeline nor a timeline.

I did 3 months of research on what system to buy (build) that can support stacking 2x49" C49RG at 5120x1440 and had my finger on the trigger to purchase a windows PC AND the M1 mini just hit the market. I was impressed with the power consumption and looked at the spec. I couldn't believe it said 2 x 5120 support. I open a chat to confirm and I asked the rep at least 3 times and said I don't believe it and s/he himself was amused that I couldn't believe it. I was assured it supports it and we are talking APPLE company. Their products go through extensive quality assurance and I was sold with the marketing. 

I ordered the 16gig 8gpu. I can't even get 1 C49RG to work. It took me 3 days just to research, buy a new cable and hold the option button down and do this and that and finally got it to come up, BUT now I have to disconnect the cable and re-connect it 2 times for the screen to wake up. 

The mini has crashed on me 2ice. *CRASH*. when did you ever hear a mac “blue screen”!? System preferences unexpectedly crashed on me. (I have screen shots) I use Visual Code for work. It crashes on me. This morning it had rebooted on me and all my apps were moved around. I don't have auto-update enabled. I tested Java on my wife's M1 laptop and it worked. But now that I use it more the memory usage all of a sudden jumps 1gig every 3 seconds and I have to kill the process with mem usage 25+ gig. 

I am disappointed. if you want a mini (M1) to just browse the web and iMessages, then go for it. M1 release is premature. not happy!  Oh not to mention my bluetooth devices connect and disconnect. My headphone & Logitech Craft keyboard doesn’t even connect. I am calling BS on Mr Cook!

I saw in another thread, that we must put this screen on HDMI 1.2 and then press a long time "Option" + click on scale in the screen parameter. Then Mac purpose (5120 x 1440) it's what I do on CRG90, and it working.

After if you change screen parameter on CRG90 (120Hz or HDMI 1.4), it still working ..... But the only way to have 5120 x 1440 in Mac screen parameter (pressing option + Click on scale), it's to put HDMI 1,2.

In the C49RG9 DisplayPort setting, I selected version 1.2 and everything works smoothly now: maxed out the resolution, albeit HDR is now only available @ 60 Hz, and no longer any trouble waking from sleep (it was always crashing).

So indeed, from the looks of things, the M1 Mini is engineered only for DisplayPort v1.2 it would seem. And if not, then it is very unfortunate that the M1 Mini handles DisplayPort 1.4 so poorly, if at all.

Thanks, that sounds hopeful! Mine still does not work with DP1.4 for me, even though I updated to the latest version of 11.2. The screen freezes for some time, becomes unresponsive at times and autosearches between different ports. So DP1.2 for me still. I guess I have the latest screen firmware (1004.0 - it seems like it is from 2019 though?).

I have found it useful to hard reset the monitor when it can’t find the monitor (this is different than not being able to handshake with the monitor. ie. if your monitor is plugged in, the monitor is set to auto find source and when you switch sources, it just rotates through the ports without stoping and trying to handshake with the screen being blank/no-backlight and the rear RGB doesn’t come on.).

This solution worked for me first time out (and is the only thing that has worked). I'll add that after following steps 1-4, if you've had your panel set to 60hz based on other troubleshooting steps, you can revert the panel back to 120hz as a step 5 and everything continues to work.

To the extent it matters, I'll add a vote for Apple to fix this issue soon!