LG UltraFine 5K Build

[Attila]

I'm running an RX Vega 64 card with the system set up as an imac Pro 1,1. Two display ports connected to the two mini-display ports on the Gigabyte Thunderbolt 3 card, and Thunderbolt 3 port out to a LG 5K Ultrafine via Thunderbolt cable.
I can get default 5K on Windows 10, but can only get a default of 2560x1440 on OSX (High Sierra 13.2). Anyone have ideas about what might be going on?

 

[Attila]

So what I did is go get an RX 480 graphics card, which I had working before and I can confirm it's still working @ 5k and the graphics card reports as the correct one in addition the monitor also reports properly:

View attachment 282198 View attachment 282197
So what I can confirm for my system on High Sierra with a GC-Alpine Ridge card installed:

1. RX Vega 64 boots to full 5k with no hardware acceleration leading to slow performance and a lot of crashes when using basic stuff like Chrome.

2. GeForce 1080 doesn't boot the monitor at all, although I can login remotely from another Mac and see what appears to be a very nice resolution, but the monitor is not recognized; I tested it out with another 1080p Dell monitor over HDMI and it worked fine.

3. An RX 580 works perfectly @5k and although some small things like brightness controls on the keyboard don't work as well as sound, none of that matters as I have external speakers and the brightness is all the way up so that works for me.

Hopefully we'll see an update that makes the Vega be able to use hardware acceleration shortly.

The top image you have, only shows a resolution of 2560x1440?

 

[joevt]

I can get default 5K on Windows 10, but can only get a default of 2560x1440 on OSX (High Sierra 13.2). Anyone have ideas about what might be going on?

Are you sure it's not a HiDPI (retina) mode? 2560 x 1440 HiDPI mode draws in a frame buffer that is 5120 x 2880.
Use SwitchResX to view the timing information for the current resolution to see exactly what's happening.

The top image you have, only shows a resolution of 2560x1440?

The image is drawn using a HiDPI mode. Open the image in a new window to see it properly.
https://www.tonymacx86.com/attachments/screen-shot-2017-09-30-at-3-44-39-pm-png.282198/
The "Displays" tab shows the screen's number of pixels.
The "System Report" shows the HiDPI resolution and not the frame buffer resolution.

 

[Attila]

Are you sure it's not a HiDPI (retina) mode? 2560 x 1440 HiDPI mode draws in a frame buffer that is 5120 x 2880.
Use SwitchResX to view the timing information for the current resolution to see exactly what's happening.


The image is drawn using a HiDPI mode. Open the image in a new window to see it properly.
https://www.tonymacx86.com/attachments/screen-shot-2017-09-30-at-3-44-39-pm-png.282198/
The "Displays" tab shows the screen's number of pixels.
The "System Report" shows the HiDPI resolution and not the frame buffer resolution.

When in the 2560 x 1440 HiDPI resolution, SwitchResX shows the pixel clock as 600MHz.

 

[joevt]

When in the 2560 x 1440 HiDPI resolution, SwitchResX shows the pixel clock as 600MHz.

600 MHz is not 5120 x 2880 60 Hz. Post a screenshot of the entire resolution timing window.

 

[Attila]

600 MHz is not 5120 x 2880 60 Hz. Post a screenshot of the entire resolution timing window.

I can do that, but here is what I am not understanding...

Right now I am back on my 4K display with a native resolution of 3840x2160. When I boot into OSX, the default resolution is again the HiDPI. But if I go into System Prefs and select scaled, I can select 3840x2160 as an option. However, when using the 5K display, the highest scaled option is only something like 3320x1890. As 5K is the native resolution of the monitor, why doesn't it show up as a scaled option in System Prefs? Basically, to put the monitor into its native 5K screen resolution, I need to use SwitchResX. Kind of makes me wonder if the new iMac Pro can display a native 5K resolution without using a tool like SwtichResX?

 

[joevt]

I can do that, but here is what I am not understanding...

Right now I am back on my 4K display with a native resolution of 3840x2160. When I boot into OSX, the default resolution is again the HiDPI. But if I go into System Prefs and select scaled, I can select 3840x2160 as an option. However, when using the 5K display, the highest scaled option is only something like 3320x1890. As 5K is the native resolution of the monitor, why doesn't it show up as a scaled option in System Prefs? Basically, to put the monitor into its native 5K screen resolution, I need to use SwitchResX. Kind of makes me wonder if the new iMac Pro can display a native 5K resolution without using a tool like SwtichResX?

Without the timing info, we have yet to prove you're actually connected as 5K.

Did you try holding the option key and clicking the Scaled button to get a list of resolutions? My Dell 5K display shows 5120 x 2880 as an option for my Titan X in at the top of the resolution list and as the "More Space" button (says "Looks like 5120 x 2880")

 

[Attila]

Without the timing info, we have yet to prove you're actually connected as 5K.

Did you try holding the option key and clicking the Scaled button to get a list of resolutions? My Dell 5K display shows 5120 x 2880 as an option for my Titan X in at the top of the resolution list and as the "More Space" button (says "Looks like 5120 x 2880")

I'll get a chance to check that out on Tuesday (currently away from home).

Here is what I remember though: if I go into the "scaled" section of Display, "More Space" comes up as a resolution of: 3360 x 1890. I did not look to see what the "Looks like" value was ---- I'll check that when I get back home on Tuesday.

 

[joevt]

I'll get a chance to check that out on Tuesday (currently away from home).

Here is what I remember though: if I go into the "scaled" section of Display, "More Space" comes up as a resolution of: 3360 x 1890. I did not look to see what the "Looks like" value was ---- I'll check that when I get back home on Tuesday.

"More Space" and "Looks Like" refer to the same thing. The different thing I want you to look at is when you hold down the option key and click the Scaled radio button. But neither of those will tell you the actual output resolution to the display. Only the timing info will.

 

[Attila]

"More Space" and "Looks Like" refer to the same thing. The different thing I want you to look at is when you hold down the option key and click the Scaled radio button. But neither of those will tell you the actual output resolution to the display. Only the timing info will.

Great; I'll check tomorrow when I am back home.

When I tried my native 3840x2160 display, the pixel clock rate was showing as 600Mhz ---- does that sound right for 4K?