Mac Pro displays issue

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Level 1

6 points

Mac Pro displays issue

Hello!

I have been trying to connect my Mac Pro to my two monitors:

1x 27 inch UHD 4K Monitor | LG 27UD59P | LG UK
1x https://www.asus.com/uk/ROG-Republic-Of-Gamers/ROG-SWIFT-PG348Q/

Now, both have only one DisplayPort but they both also have HDMI.
I'm sharing these two monitors between the mac and my gaming PC, and the PC is using the DP inputs on both monitors.
I intend to connect the Mac Pro to a HDMI port on each monitor and be able to simply switch inputs on them, and voila, I have both computers on the same desk.

The cables I'm using are:

1x HDMI - HDMI cable

1x MiniDisplayPort - HDMI cable

The issue is, the HDMI-HDMI cable works on either monitor, connected to the Mac Pro's full size HDMI port.
But the other cable won't work. On the LG monitor, nothing shows up. On the ASUS one, I see a weird green blotch on top of what should be the desktop, and it blinks on and off.

Now the reason I'm thinking about is the refresh rate.
Now, the LG page says this monitor is capable of 56Hz ~ 61Hz Vertical refresh rate.

The ASUS one has different supported refresh rates depending on the input, so for HDMI it's 24Hz ~ 60Hz.

Since the Mac Pro works with BOTH of them if I just use the HDMI cable, I'm assuming the Mac Pro is sending out a signal that's somewhere in between the two monitors' supported refresh rate.

Which means the second input, via thunderbolt port should also work.

But it's not working. I've tried to connect it to both monitors, both by itself and with the HDMI cable also connected.

When I have both cables connected to both monitors, the Mac does detect a second monitor and extends the desktop but I can't see anything on the second screen.

This leads me to think it might be the CABLE. I only have one of this cable here so I can't test this.

So I need to know if there's something else I could check and test before buying a new cable, AND if I do buy one, what do I look for to make sure I'm buying the correct cable?

Thanks in advance!

Mac Pro, macOS Mojave (10.14.1), 12-core, 64GB RAM, 1TB PCIe Storage

Posted on Nov 14, 2018 4:49 PM

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Answer 1

Best reply

John Lockwood

Level 6

13,685 points

Nov 24, 2018 12:51 PM in response to baterax

You don't say which model of Mac Pro you have but it probably does not matter.

The 'new' Mac Pro 2013 only has a HDMI 1.2 port which means it does not support 4K resolution at 60Hz. Apparently also the Mac drivers do not support 4K over a HDMI 2.0 port in a 'classic' Mac Pro even if the PCIe video card supports it.

What you should be able on both the current and older Mac Pro models is to get a Mini Displayport to HDMI 2.0 adapter. HDMI 2.0 does support 4K at 60Hz. See - https://www.club-3d.com/en/detail/2339/mini_displayport_1.2_to_hdmi_2.0_active_a dapter/

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Answer 2

Nov 24, 2018 2:38 PM in response to baterax

If you are using one of the scaled modes then this is how an Apple 'retina' display behaves. See my previous post here for a lot of details about this - Re: Any Way To Change Screen Resolution Based On Content?

So to summarise the 'apparent' resolution maybe lower to make the text bigger but it uses the extra resolution to smooth the text. It should also display other non-scaled items like photos and videos at full resolution regardless of the amount of scaling.

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Answer 3

baterax Author

Level 1

6 points

Nov 24, 2018 12:51 PM in response to John Lockwood

It’s the late 2013 model.

But you are correct.

I tested it with a minidisplayport to DisplayPort cable and it worked.

Guess now I need either a cable like you suggested, or a DisplayPort switch...

Thanks!

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Answer 4

Nov 16, 2018 2:46 AM in response to baterax

If you get the Mini Displayport to HDMI adapter I mentioned then you can have the Mac connected via (effectively) HDMI to the displays, and the PC via the monitors Displayport connection.

The Club-3d adapter will be cheaper than buying a switch box.

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Answer 5

baterax Author

Level 1

6 points

Nov 24, 2018 12:53 PM in response to John Lockwood

So, I have a new problem now.

I bought the suggested adapter, and everything now works.

BUT

The 4K display has one issue still. If I set it to actual 4K (using the Option+click on "scale" trick), everything displays too small.

Using scaled mode, the monitor is actually at 2560x1440. So I'm wasting half my screen. Unacceptable.

How can I use it in native 4K but have things at their normal sizes?

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Answer 6

Nov 24, 2018 5:00 PM in response to baterax

Using scaled mode, the monitor is actually at 2560x1440.

If I am understanding this whole retina display thing correctly, the monitor is set to its full resolution, and the text is drawn so that it "looks like" 2560 by 1440, by drawing it 2:1 size. (if it were drawn 1:1 at full resolution, it would be so tiny you could not read it.)

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Answer 7

baterax Author

Level 1

6 points

Nov 24, 2018 5:34 PM in response to Grant Bennet-Alder

That is exactly what it's doing.

But what bothered me is:

I was editing video in Premiere. I use the Ultrawide for the real estate, and the 4K for my reference monitor.

When I looked at the settings, Premiere saw it as 2560x1440.
So I'm worried I'm not seeing 4K here. This could seriously ruin my workflow. And I definitely can't set it to 4K because then everything is so tiny I can't use it.
Also on Youtube, when viewing content, it detects the resolution... It doesn't see it's 4K. I have to set it manually and I'm not sure it's actually doing it!
Ugh. I use these same two monitors on Windows and I don't have this problem on there (I do have several other ones though... for example Windows doesn't know how to handle the two different resolution screens so if I drag something from one to the other, all **** breaks loose. But I digress)...

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Answer 8

Nov 25, 2018 3:07 AM in response to baterax

Applications need to be written to take advantage of Apple's Retina display capability. (Also known as HiDPI mode.) Adobe did this in Adobe Premiere Pro CS 6.0.2. See - https://www.videoguys.com/blog/adobe-premiere-pro-cs6-now-fully-supports-retina- macbook-pro-both-hidpi-and-gpu-compute/

So make sure you are using at least that version.

You may also need to do some extra steps to enable HiDPI mode for your monitor. Some monitors come pre-enabled in some versions of macOS, for example the Dell P2415Q was enabled a long time ago. I linked to articles on how to enable HiDPI mode and how to configure HiDPI resolutions in my previous replies. You might also want to get the Pro version of this tool - http://displaymenu.milchimgemuesefach.de/ as it will make it easier to see which resolutions are enabled for HiDPI mode.

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Mac Pro displays issue

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