problems with running two monitors with my MacPro....the round one.

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Level 1

9 points

problems with running two monitors with my MacPro....the round one.

I have a MacPro purchased in 2015. I use two Samsung s27d360 monitors. Frequently one will flash a number of times and then go black. Sometimes both will flash on and off. Sometimes when one is black the cursor will travel over as if monitor is still on....sometimes not. I have changed cables and plugged into the back of the Mac many different configurations and all same results. I have even purchased two new monitors and they did it right away. I also bought Apple cables and the same result. This computer has been sent off 3 times with all parts supposedly replaced and still does the same. I have video that I will try to insert but who knows. This MacPro should be able to run 6 monitors. Has anyone ever had a similar issue? Could not insert video.

Posted on May 27, 2019 10:18 AM

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Answer 1

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John Lockwood

Level 6

13,691 points

May 28, 2019 2:43 AM in response to rain_h2o

There are two potential issues when connecting two HDMI displays to the round Mac Pro aka Mac Pro 2013 aka MacPro6,1.

The first issue is that if you want to connect two HDMI displays as long as they are 1080p displays you can do this in theory without an active adapter but you must ensure that one is plugged in to the built-in HDMI port and the other is plugged in to either Port 1, 2, 3 or 4 but not ports 5 or 6.

See - https://support.apple.com/en-gb/HT202801

The second issue is if you are using a 4K HDMI display then you really should use an active Mini Displayport to HDMI 2.0 adapter. In theory the built-in HDMI port and most passive adapters can do 4K but only up to 30fps and not the full 60fps.

If you want to use three or more HDMI displays of any resolution then you must to use active adapters.

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Answer 2

May 27, 2019 11:44 AM in response to rain_h2o

Those are "ordinary" 1080p monitors with HDMI and VGA inputs. I presume you are using HDMI (if not, you should be).

The Mac Pro was built for DisplayPort displays, which use far lower voltages. By the time you attach three "legacy" displays to any ports in any combination, the signal levels are pulled so low and one or more of the displays always drop out due to low voltages in the signals. (The built-in HDMI port counts as one passive display if you connect anything to it.)

You could be encountering the same problem, just a little sooner that typical.

The solution for three display is to use at least one ACTIVE Mini DisplayPort to HDMI adapter. An ACTIVE adapter is a little more expensive because it has signal re-drivers in it. Electronics in the adapter is powered by a voltage from the interface to re-drive crisp new signals at the levels expected by your "legacy" HDMI display.

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Answer 3

rain_h2o Author

Level 1

9 points

May 27, 2019 12:52 PM in response to Grant Bennet-Alder

I only use two monitors but I presume the answer will be the same. I am impressed if this works. I cannot tell you what I have been thru with this issue. So what you are saying is that I need two active adapters to use with the hdmi cables to hook up to two of the six mini's? Or continue with one hdmi out of the Mac and one active adapter.?

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Answer 4

May 27, 2019 9:57 PM in response to rain_h2o

It always drops out when you connect three.

Many people 'get away with' two, but you are using two identical displays, and all it takes is them being a little more temperamental than typical and one will drop out.

You should be able to use one ACTIVE adapter, and the built-in HDMI.

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Answer 5

rain_h2o Author

Level 1

9 points

May 28, 2019 1:14 PM in response to Grant Bennet-Alder

I really appreciate the input....and so quickly. I will buy two active adapters since I forgot to mention there were times where I had only one monitor going and it would act up all by itself....so it looks like these monitors are very needy. The cost is not too bad....17 bucks or so each assuming I have the right gizmo. I will order and follow up on the post soon. Thanks.

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Answer 6

rain_h2o Author

Level 1

9 points

May 28, 2019 1:18 PM in response to John Lockwood

Thank you for your response. Making sure the monitors were on different bus was addressed early on but still did not fix the issue. It does sound like the active adapter is the solution....it makes complete sense. Can't believe the Apple Geniuses's could not come up with this solution.

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Answer 7

rain_h2o Author

Level 1

9 points

Jun 4, 2019 2:33 PM in response to John Lockwood

It has been 5 days with the two active adapters and I have not had one hint of an issue to this point. Once again I appreciate the help with this issue.

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Answer 8

Jun 7, 2019 6:33 AM in response to John Lockwood

Thanks to this thread and the link to Thunderbolt configurations I no longer have a 5K monitor which blinks on and off incessantly which I'm trying to work with photo images.

Thanks, John.

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