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mightyjabba

macrumors 68000
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Sep 25, 2014
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I upgraded from a 2014 MacBook Pro that I used in clamshell mode connected to a mouse, keyboard, lots of USB peripherals, and 3 external displays (non-retina ones). This wasn't a perfect setup -- I would occasionally have all of my USB devices die for what I think are power-related reasons, but I didn't have any major issues with reliability. I knew that switching over to a new MacBook Pro would be difficult. I had been running High Sierra on the 2014 because it was stable and hadn't caused any problems for me, and the new computer would come with Catalina, which has its own challenges. I knew I would also have to find USB-C alternatives for connecting my peripherals. But the 16" MacBook Pro seemed improved enough to make it worth the trouble. However, I've been having a lot of issues trying to slot it into my current desktop setup. (I decided to set up the new computer fresh instead of using Migration Assistant in the hopes of avoiding problems, BTW.)

It took a lot of experimentation to get all 3 displays working at the same time, and even after I thought I had it, one or more of them will sometimes not wake up after sleep, requiring me to unplug and replug. My desktop wallpaper will spontaneously reset on one or more the monitors for no apparent reason. I have also had the computer shut down while in sleep or have trouble waking up when the monitors are connected (all of them just sort of blinking on and off). I've also had USB disconnects at a considerably higher rate than before. My Logitech M705 mouse's cursor was intermittently jerky until I moved the receiver to a different hub that was farther away from the rest of my setup, so I'm guessing there was some kind of interference. The point is, my experience with the computer so far has mostly involved trying to squash these kinds of bugs.

Some of this may be due to the HP Thunderbolt Dock 120W G2 that I was trying to use. I got a good deal on it second-hand, and while it does appear to work fine for a while, it is flakey. However, I am not sure that all of these problems can be attributed to it. I only have one monitor attached to it (since more than that won't work) but I still have problems with the monitors connected directly to the computer. I also think that most of these issues can probably be attributed to Catalina and or USB-C/Thunderbolt rather than the MacBook Pro itself, but that's kind of academic.

Is there anyone who has two or three monitors connected to a 16" MacBook Pro with rock-solid reliability? I am willing to get a different dock/hub if necessary. I'm also considering going with a very large Ultrawide display if that might simplify matters. Any input would be appreciated.
 
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CalDigit. Do not commingle running displays off USB-C hubs. Use a Thunderbolt 3 dock to run 2 displays and whatever USB peripherals you need. Then use a USB-C to DisplayPort cable, or whatever interface is needed to directly connect the 3rd display to the machine.
 
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I cannot get 2 4K displays to work in clamshell mode at all, no matter what I try (so far). Hooked both directly to the laptop, screens unresponsive. Hook them up via a CalDigit TS3+ dock, same. If I set the resolution to anything scaled they won’t even display a picture in clamshell mode. Just black screen. Need to hard reboot the Mac every time. And even with the lid open, the displays work, but machine will not wake from sleep. (I have the i9 2.4ghz model with the 8GB GPU). Hopefully this can be fixed with an update soon.

same screens worked fine on my 2018 15”

(Someone in the dock thread said the new Targus dock works for them. I may get one and give it a try)
 
I cannot get 2 4K displays to work in clamshell mode at all, no matter what I try (so far). Hooked both directly to the laptop, screens unresponsive. Hook them up via a CalDigit TS3+ dock, same. If I set the resolution to anything scaled they won’t even display a picture in clamshell mode. Just black screen. Need to hard reboot the Mac every time. And even with the lid open, the displays work, but machine will not wake from sleep. (I have the i9 2.4ghz model with the 8GB GPU). Hopefully this can be fixed with an update soon.

same screens worked fine on my 2018 15”

(Someone in the dock thread said the new Targus dock works for them. I may get one and give it a try)
I’m running 1 4K in clamshell, no problems. Can you at least get a single display running. I’ve had to unplug my dock once because the display wouldn’t wake from sleep, definitely software bugs.
 
CalDigit. Do not commingle running displays off USB-C hubs. Use a Thunderbolt 3 dock to run 2 displays and whatever USB peripherals you need. Then use a USB-C to DisplayPort cable, or whatever interface is needed to directly connect the 3rd display to the machine.

Which CalDigit dock do you have? And you're able to run two displays from it? I was really hoping to be able to get everything down to a single cable or maybe two, but since the HP dock doesn't seem to work with more than one display or supply enough power, I'm stuck with all four of my ports full.
 
I’m running 1 4K in clamshell, no problems. Can you at least get a single display running. I’ve had to unplug my dock once because the display wouldn’t wake from sleep, definitely software bugs.
Yes, 1 works fine. 2 is where the problem is. And I’ve tried with both a DisplayPort to USB-C cable and a DisplayPort into the CalDigit adapter, doesn’t make a difference.
 
Does it make a difference if you try it in normal mode, so not in clamshell?
 
I'm not entirely sure. I haven't done a lot of testing, but I did run it open for the first day or two and I wouldn't say it was problem-free.
 
I was only asking because in the past I've had lots of inconsistent issues with MBPs and external monitors when running in clamshell mode, particularly with the recent MBPs. I lost count of how many docks and cable combos I had to try to get it working reliably a couple of years ago.
 
I understand. The frustrating thing is that I'm coming from a setup that was completely reliable (more or less), so I'm really starting to wonder what the point of this upgrade was for me. The difference in performance for most tasks isn't really even that big, and I'm adding an element of instability. I think it would be perfectly fine if I was just using it on its own, though.
 
I'm going to try and run this without the HP dock, and just use a small Lenovo USB-C hub that has one HDMI port and some USB-A ports. I am starting to feel like the dock may be the source of many of these issues.
 
I've been running with the above setup for more than a day and have had absolutely no issues, so I'm fairly confident the HP dock was the source of my problems. I was this close to just returning the new machine. It's actually working just fine with the Lenovo hub I've been using (this one), so I guess I'll stick with that for the moment.
 
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I've tried two different thunderbolt docks with dual 1080p displays. The CalDigit Minidock HDMI version and a no name chinese dual hdml thunderbolt dock. Both of them work ok except they won't wake up from sleep. I was using it fine with my 2017 15 inch mbp on catalina, but after upgrading the the 16 inch it has the problem every time it wakes from sleep. Unplugging the dock and plugging it back has been working to wake up the displays.
 
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@fishkorp What kind of display do you use? My work setup is a 16" MacBook Pro connected via displayport to an Asus 4k monitor which also crashes after the display wakes up from sleep. Wondering if it's just with that type of screen or a general issue with external displays.

As a workaround I've disabled power and just use a simple screensaver to lock the display, but this worked fine on my previous MbP.

Anyway, does your 'console' app also show a crash in CoreGraphics?
I've reported this issue to Apple, but the feedback site says there are no similar bugs...
 
@fishkorp What kind of display do you use? My work setup is a 16" MacBook Pro connected via displayport to an Asus 4k monitor which also crashes after the display wakes up from sleep. Wondering if it's just with that type of screen or a general issue with external displays.

As a workaround I've disabled power and just use a simple screensaver to lock the display, but this worked fine on my previous MbP.

Anyway, does your 'console' app also show a crash in CoreGraphics?
I've reported this issue to Apple, but the feedback site says there are no similar bugs...
I have 2 different displays. One is an LG, the other a Monoprice.
I haven’t checked for crash logs. Apple support has a ton of data from the diagnostic tool they had me run and send them (was about 500MB in size). They should be getting back to me any day now.
 
I have 2 different displays. One is an LG, the other a Monoprice.
I haven’t checked for crash logs. Apple support has a ton of data from the diagnostic tool they had me run and send them (was about 500MB in size). They should be getting back to me any day now.

Seems like the 10.15.2 update released today solved this problem for me.
 
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I've been running with the above setup for more than a day and have had absolutely no issues, so I'm fairly confident the HP dock was the source of my problems. I was this close to just returning the new machine. It's actually working just fine with the Lenovo hub I've been using (this one), so I guess I'll stick with that for the moment.

What you were trying to do with the HP G2 dock, it's a known issue with that particular dock and multiple external displays. I don't think it has anything to do with the 2019 Macbook Pro, or OSX, or clamshell, or your monitors or cables. I definitely think it's the dock. See, e.g., Multiple External Displays through Thunderbolt Dock G2, and HP Thunderbolt Dock 120W G2 Displayport/External Monitor Flicker.

I tried to run an older Apple LED Cinema Display (the older mini displayport) using the 2019 16" Pro. Fired right up. I've got an UpTab adapter that lets my 2017 iMac Thunderbolt Port drive this old AC LED Display, it was like the only one that worked, several others failed.
 
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I did find people who were supposedly using it successfully on the Mac before I bought it, but I do think the dock is the problem, which I why I stopped using it
 
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I'm not so sure.
I just upgraded from a 2018 15" to a 2019 16". I have a Dell WD15 USB-C dock both at home and at work. I've been using this setup for quite some time with no problem on the 15", but now with the 16", the display flickers. It's like a very quick connect/disconnect once every 5-10 seconds. Totally unusable.
I updated the Dock to the latest firmware but no difference.
 
I'm having a similar issue with the LG Ultrafine 5K display. Occasionally upon waking from sleep both the 16" MacBook Pro display and the LG display will flicker continually until I unplug the external display. Once it happens I am not able to get the external display to connect again without restarting the laptop.
 
To give a completely different option. I use a sonnet egpu puck and connect all my 3 monitors to it. It works beautifully all around on the 16 inch.
stable and keeps the machine cooler too. Something to consider
 
That’s great and all, but I draw the line at spending $400 to $500 for this. For the record, my simple Lenovo USB-C hub with HDMI has been working flawlessly since I switched over to it. I do have to plug in four cables when I dock the machine but I think I can deal with that.
 
For those not using Thunderbolt 3 docks to connect their displays, do not use USB-C hubs/docks in-between the computer and the displays. Instead, directly connect displays with USB-C <-> DisplayPort/HDMI cables between the computer and display. When doing this, the computer switches that port into USB-C Alt Mode, which no longer makes it a USB port, but a dedicated non-USB port for carrying native display signals from the GPU to the display. When using a USB-C hub, the total bandwidth available to the hub is shared between all devices connected to that hub, in addition to routing a video signal, which in itself may be inadequate to drive the display(s) at its native resolution and refresh rate (and/or lead to other complications).

USB is CPU-dependent, so the more USB devices are connected to your computer and doing something, the harder the processor has to work to communicate with all of them (more heat and noisier fans).

While showing stats are helpful in diagnosing problems, it's also just as important to describe how exactly the displays are connected to the computer. Listing your setup in the signature section of your profile will help others help you faster, all while avoiding the need to repeat yourself.

More information:

HDMI Alt Mode for USB-C
DisplayPort Alt Mode for USB-C
USB-C to DisplayPort Cable (Example)
USB-C to HDMI Cable (Example)
 
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