Three monitors not working on Mac pro 5.1

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Level 2

348 points

Three monitors not working on Mac pro 5.1

I have a mid 2012 mac pro tower with Sierra 10.12.6 with an ATI Radeon 57702 graphics card which is supposed to support 3 monitors. I am using this computer in my recording studio . It has been working fine with two Acer 27" G246HL monitors for a few years . These monitors are aways from the computer and are connected to one DVI port adapter to a 20ft vga cable and the other to a mini display port to vga adapter to vga cable.

I recently purchased a LG ultra wide 34UM64 wide screen monitor to add as a 3rd monitor for more windows to be open, It has a resolution of 2560x1080 but defaults to 1960 x1080 which I can live with since I am not a graphics designer but it would be nice to get the full resolution .

It is connected with a 15 ft Mini display port to HDMI cable.

However, my main concern is I only am able to have two monitors show up under displays in my systems prefs. Either the two Acer or one Acer and the LG ultra wide depending on which one is turned on first .

Shouldn't this card be able to support 3 monitors or am I missing something here? Di I need another card ? Are there any other solutions to get all three monitors working together?

TIA, Craig

Mac Pro 5.1(Mid 2012) Sierra 10.12.6

2 x 3.33GHz 6 core Intel Xeon

64GB ram

ATI Radeon 5770 1024mb

Posted on Jan 5, 2019 10:53 AM

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Answer 1

Best reply

lllaass

Level 10

210,417 points

Jan 5, 2019 12:06 PM in response to Craig

See:

ATI Radeon HD 5770 and 3 monitors : 2x mi… - Apple Community

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Answer 2

Craig Author

Level 2

348 points

Jan 5, 2019 7:25 PM in response to lllaass

Thanks for the link ! I'm not sure what would work better for me the DVI or HDMI active adapter as I will need a 20ft dvi or hdmi cable as well . The third monitor LG ultra wide 34UM64 wide screen monitor has both types inputs.

21:9 UltraWide, 2560 x 1080 5ms Response Time at 60Hz Refresh Rate

2 x HDMI, DisplayPort, DVI Mac Compatible with speaker

So perhaps one of these might solve the problem ?

https://www.amazon.com/Cable-Matters-DisplayPort-Supporting-Technology/dp/B00EDSZYII/ref=sr_1_3?ie=UTF8&qid=1546741567&sr=8-3&keywords=mini+displayport+to+dvi+adapter+active

or

https://www.amazon.com/Cable-Matters-DisplayPort-Supporting-Technology/dp/B00PJ3LSIG/ref=pd_bxgy_23_3?_encoding=UTF8&pd_rd_i=B00PJ3LSIG&pd_rd_r=c792b4d6-115a-11e9-a0b8-adad1f45e97c&pd_rd_w=mRiQs&pd_rd_wg=hjciM&pf_rd_p=6725dbd6-9917-451d-beba-16af7874e407&pf_rd_r=WJ1FCTTQQ4F6PX8E1NTC&psc=1&refRID=WJ1FCTTQQ4F6PX8E1NTC#customerReviews

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Answer 3

lllaass

Level 10

210,417 points

Jan 6, 2019 12:48 AM in response to Craig

I would try the DVI active adapter.

My concern is that your cable lenght may be contributing to the paoro and you may need an adapter with aux power like

https://www.amazon.com/StarTech-com-MDP2DVID-DisplayPort-Dual-Link-Powered/dp/B004I6L6DW

Since the previous Community [pst I linked to stated that the card does not have a lot of power just using an active adapter that does not use aux power may not be sufficient.

In the active adopters in your links are cheap I would try it.

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Answer 4

Craig Author

Level 2

348 points

Jan 6, 2019 7:27 PM in response to lllaass

I ended up ordering the both of the active mini display to DVI and HDMI adapters as well as some higher grade cables for the length . I figured I could use them on both of display ports on the Mac pro to see if might help . I am hoping this will get all three monitors up and running as wells the 2560x1080 wide screen resolution for the LG before going for more expensive solutions.

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Three monitors not working on Mac pro 5.1

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