Selecting Which Video Card The Monitor is On (2013 Mac Pro)

Question

Selecting Which Video Card The Monitor is On (2013 Mac Pro)

I know this sounds like an odd question but I just a got a new (to me) 2013 Mac Pro that has the dual video cards. I have two problems that I am trying to resolve, but around how to select which monitor is powered by which of the two video cards in the system.

My first problem is that I have three displays, one is an older Cinema display that I have oriented in portrait mode and when I boot the Mac this becomes the primary screen (shows the Apple loading bar) and it of course shows it sideways. Second is that one of the reasons I got this Mac was so that I could put two monitors on one card and have one monitor on the other card so that that monitor was not "sharing" resources with the other two.

When I look at system profiler I see that all three are on the same card and I've moved the plugs around and can't seem to find a way to get my monitors set up the way I want them (and to set the primary monitor to not use my one monitor that is in portrait mode)?

Mac Pro, OS X Yosemite (10.10.1), Late 2013 / 32GB RAM / 256GB SSD

Posted on Jan 20, 2015 11:52 AM

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Answer 1

Jan 20, 2015 12:03 PM in response to craigfromdenver

The Mac Pro late 2013 has all the display Interfaces on one of its two graphics cards, by design. The second card is used for high-speed, uninterrupted GPU computation. There is no way to allocate graphics interfaces between the cards. If you had six displays attached, they would all be on one card. It is also not the slightest bit taxing to have it set up this way.

If you would like to change the primary/startup display, use the arrange pane of Displays Preferences:

Each of the elements show there is an Icon. Screens are shown at their relative sizes in pixels, and in their logical positions in space, and should be dragged to correspond to their positions on your bench if you want to use them as a contiguous extended desktop.

The tiny white strip at the top of one of the displays is the MenuBar icon. Drag that to the display you want to be primary.

One additional item -- if you drag and drop one display over another, it will enable mirroring on those two displays (only).

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Answer 2

lllaass

Level 10

210,513 points

Jan 20, 2015 12:38 PM in response to craigfromdenver

In this Apple Article

http://support.apple.com/en-us/HT202801

it implies that which one shows at bootup can't be selected:

Which displays are active during startup?

Usually only one connected display will illuminate until OS X is finished starting.

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Answer 3

Jan 20, 2015 12:33 PM in response to Grant Bennet-Alder

I already did what you showed in your screenshot, my bar is on the monitor that I want to be the primary and the portrait monitor is still the "boot" monitor.

I'm surprised there is not way to choose the card for the monitor but if it's optimized the way you implied then I'm not going to worry too much about it. The booting issue is still an issue for me though.

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Answer 4

Mar 14, 2015 6:30 PM in response to craigfromdenver

I would also add using a different Thunderbolt port for each display, even though they are all on one GPU, is optimal. The set up of the ports is a little strange, top two left vertically, top two right vertically and bottom pair horizontally are the pairs for each of the three ports, 0 through 2..

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Answer 5

lllaass

Level 10

210,513 points

Mar 15, 2015 2:20 AM in response to Digitalclips

Using different Thunderbolt buses is discussed here

Mac Pro (Late 2013): Using multiple displays - Apple Support

as is is which TB pores connect to which TB bus

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