Cannot set desktop for 2nd monitor for Mac Pro (2019)

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Cannot set desktop for 2nd monitor for Mac Pro (2019)

I have the new Mac Pro (2019) and have it set up with two monitors (Apple LED Cinema Displays.) Both work well except I cannot set the desktop background for the 2nd monitor. I set it daily and upon starting the next day, it starts with the same background as the main monitor, no matter what I set it for.

I'm assuming its a Catalina issue as I don't have the issue with my previous 2012 Mac Pro. If it helps, this Mac Pro was set up using the Time Machine backup from the previous Mac Pro so maybe it's confused looking for the hard drive of the previous Mac Pro (I saw this in another thread and tried it's remedy, which didn't work.)

The other frustrating thing is when the Mac Pro boots up, the welcome/log on screen appears on the 2nd monitor and never the main, regardless of which port I'm using (which are the TB3 ports. I hope to have HDMI to mini-display adapters in soon and will use HDMI instead.) Once I log in, all reverts to the main monitor but its a bit disconcerting as well. I do not mirror the monitors and doing the Gather Window does not help either.

Thanks so much!

Posted on Aug 17, 2020 3:15 PM

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Answer 1

Aug 17, 2020 4:43 PM in response to Albeer

This is a graphic of the Arrangement pane for "Extended Desktop", a popular way (but not the only way) to use your multiple screens. The displays are concatenated along an Edge, and the mouse can move freely across the virtual divider, and can carry a window with it. The simulation is so good, you can park a window half on each display, and when you scroll that window, the two halves will scroll perfectly in Sync.

Note that the blues Box are Icons that can be re-arranged so that the displays correspond with their positions on your work surface.

The tiny MenuBar Icon can also be dragged to a different display. The display you drag it to will be the "primary" display, and will be used for startup screens.

Since all displays are part of one "extended desktop" attempting to set separate backgrounds for different displays has no meaning. There is ONE extended desktop, and it extends over all the displays.

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The alternative method is called "Displays have Separate Spaces". You use Mission Control to agglomerate applications and windows used at the same time, and collect those into "Spaces". A simple generalization of that concept allows you to assign different spaces to different displays. No dragging between displays, unless you use Mission Control to move items between Spaces, and therefore indirectly onto another display.

It's your choice. which way would you like to use your multiple displays?

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Answer 2

Aug 24, 2020 11:24 AM in response to Albeer

Do you intend to be using "Extended desktop", or is each display intended to be a world of its own (separate Spaces)?

You complained that the "Primary" display did not stick, and I provided the mechanism for setting the primary Display -- the tiny MenuBar Icon.

Using DisplayPort family Vs HDMI will not change your fundamental complaints about interactions between displays.

I do not understand why you are trying to hunt down HDMI adapters when you already have ThunderBolt/USB-C ports available. These are very close the DisplayPort family already, and attempting to convert to HDMI is a giant step backward -- HDMI is slower, does not work well at high resolutions, and uses more power.

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Answer 3

Aug 24, 2020 1:32 PM in response to Albeer

If you intend to use Extended desktop, Be sure to uncheck this box:

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Answer 4

Albeer Author

Level 1

131 points

Aug 24, 2020 9:01 AM in response to Grant Bennet-Alder

Hi Grant,

Your explanation, while fascinating reading, does not address my issue. I am very much aware of how Apple monitor screens work and how the blue boxes align, and MenuBars can be assigned and so forth.

However, I have been using separate images between the same two monitors since before Mac OS Sierra and NEVER had this issue. The only difference now is the Captiva OS and-- what I believe to be the culprit-- is that I'm using the USB-C (Thunderbolt 3) ports for my Apple Cinema Displays (per Apple's direction.) This Mac Pro came with HDMI display ports for the AMD Radeon Pro 580X graphics card output but I cannot find a suitable HDMI male to mini-display port female adapter. I did locate and try the QGeeM 20Cm 4K x 2K HDMI to Mini DP Adaptor from Amazon and no dice. If anyone knows of such an adapter that worked for them, I'd like to know about it. Thanks so much!

https://www.amazon.com/DisplayPort-Converter-QGeeM-Compliant-Dual-Mode/dp/B07H29J86N/ref=cm_cr_arp_d_product_top?ie=UTF8

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Answer 5

Albeer Author

Level 1

131 points

Aug 24, 2020 1:28 PM in response to Grant Bennet-Alder

Do you intend to be using "Extended desktop", or is each display intended to be a world of its own (separate Spaces)?

It would be the Extended desktop as the separate spaces does not afford what I'm using the monitors for.

You complained that the "Primary" display did not stick, and I provided the mechanism for setting the primary Display -- the tiny MenuBar Icon.

The Primary display does stick, with some respects, but not every time I start the machine. (And yes, I use the MenuBar icon.) However, my concern is I cannot get either the Primary nor Secondary display backgrounds to stick. Every time the Mac Pro starts, it is the Catalina Dynamic Desktop on both monitors and no matter if I change either monitor to another desktop picture, it resorts to the Catalina Dynamic Desktop upon restart.

Using DisplayPort family Vs HDMI will not change your fundamental complaints about interactions between displays.

I am thinking of using the HDMI ports as that is what Apple provides for this Mac Pro model per the AMD Radeon Pro 580X card. Why not DisplayPort or mini-display or something else, I don't know. I asked a Apple Tech Support rep today and even she was flummoxed. I totally agree HDMI is probably not the best option but why not use if Apple provided it? (This Mac Pro cost so much, I didn't have the funds to buy new ones.)

I do not understand why you are trying to hunt down HDMI adapters when you already have ThunderBolt/USB-C ports available. These are very close the DisplayPort family already, and attempting to convert to HDMI is a giant step backward -- HDMI is slower, does not work well at high resolutions, and uses more power.

Yes, I AM using the Thunderbolt 3/USB-C ports for the displays but that ties up two TB 3 ports with monitors that I'd rather be using for data. And the Apple Support rep agreed. But had no solution.

I can live with the same background on both monitors, I just thought maybe someone else experienced the same thing and offered an option. I appreciate your input.

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Cannot set desktop for 2nd monitor for Mac Pro (2019)

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