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adergaard

Member

Registered: 2016-07-27

Posts: 14

iMac 5k resolution not an option?

I'm running Arch on an iMac late 2014 so called "5k" version i.e. a native resolution of 5120x2880.

This resolution is not available to me in Arch.
Running hwinfo I get the following as pertaining to the display:

40: None 00.0: 10002 LCD Monitor
  [Created at monitor.125]
  Unique ID: rdCR.eLNldlOWcj6
  Parent ID: VCu0.0N2Uem8f9GE
  Hardware Class: monitor
  Model: "Apple iMac"
  Vendor: APP "Apple"
  Device: eisa 0xae01 "iMac"
  Serial ID: "39017C76DCA26"
  Resolution: 2560x1440@60Hz
  Resolution: 3840x2160@60Hz
  Size: 597x336 mm
  Year of Manufacture: 2014
  Week of Manufacture: 12
  Detailed Timings #0:
     Resolution: 3840x2160
     Horizontal: 3840 3888 3920 4000 (+48 +80 +160) -hsync
       Vertical: 2160 2163 2168 2222 (+3 +8 +62) +vsync
    Frequencies: 533.25 MHz, 133.31 kHz, 60.00 Hz
  Year of Manufacture: 2014
  Week of Manufacture: 12
  Detailed Timings #1:
     Resolution: 2560x1440
     Horizontal: 2560 2608 2640 2720 (+48 +80 +160) -hsync
       Vertical: 1440 1443 1448 1481 (+3 +8 +41) +vsync
    Frequencies: 241.50 MHz, 88.79 kHz, 59.95 Hz
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #36 (VGA compatible controller)

I'm at loss as to where to start looking for how to fix this, or maybe it is not supported?

Please do let me know if you need me to run any commands and paste the output here in order for you to better help.
Thanks.

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: iMac 5k resolution not an option?

What does xrandr say?

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adergaard

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Registered: 2016-07-27

Posts: 14

Re: iMac 5k resolution not an option?

What does xrandr say?

➜  ~ xrandr
Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 16384 x 16384
eDP-1 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   3840x2160     60.00*+
   3200x1800     59.98  
   2560x1440     59.95  
   2048x1536     60.00  
   1920x1440     60.00  
   1856x1392     60.01  
   1792x1344     60.01  
   1920x1200     59.88  
   1920x1080     59.96  
   1600x1200     60.00    59.87  
   1680x1050     59.95  
   1400x1050     59.98    59.98  
   1280x1024     59.89    60.02  
   1440x900      59.89  
   1280x960      60.00    59.94  
   1280x854      59.89  
   1280x800      59.81  
   1280x720      59.86  
   1152x768      59.78  
   1024x768      60.04    60.00    59.92  
   960x720       60.00  
   928x696       60.05  
   896x672       60.01  
   800x600       60.00    60.32    59.86    56.25  
   848x480       59.66  
   700x525       59.98  
   720x480       59.71  
   640x512       60.02  
   640x480       60.00    59.94    59.38  
   512x384       60.00  
   400x300       60.32    56.34  
   320x240       60.05  
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)
DP-3 disconnected (normal left inverted right x axis y axis)

jasonwryan

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From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: iMac 5k resolution not an option?

https://wiki.archlinux.org/index.php/Xr … esolutions

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adergaard

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Registered: 2016-07-27

Posts: 14

Re: iMac 5k resolution not an option?

https://wiki.archlinux.org/index.php/Xr … esolutions

While I appreciate the link, I really do, the link states the following:

Once a suitable resolution is found using xrandr, the mode can be permanently added by creating an entry in /etc/X11/xorg.conf.d/:

My feeling here is that xrandr isn't finding any suitable resolution i.e. 5120x2880, it finds a max resoltuion of 16384x16384 (which seems like some default upper value if none is found) and then it has a whole list of presets, as you can see from above.

Perhaps I'm missing something here? Do you mean to suggest that I can just manually add a /etc/X11/xorg.conf.d/10-monitor.conf anyways with the 5120x2880 values anyways?

Thanks again for taking the time.

Last edited by adergaard (2017-02-15 19:02:12)

loqs

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Registered: 2014-03-06

Posts: 18,082

Re: iMac 5k resolution not an option?

Xrandr#Adding_undetected_resolutions

adergaard

Member

Registered: 2016-07-27

Posts: 14

Re: iMac 5k resolution not an option?

Addendum

I just realized that I'm using the xf86-video-ati driver whereas my video card, in the iMac, seems to be the so called Tonga (R9 285).
From what I understand xf86-video-amdgpu is for GCN1.2 cards only which includes the Tonga (R9 380/X, R9 285).

Could this be relevant? Should I switch driver to use the amdgpu one instead?

adergaard

Member

Registered: 2016-07-27

Posts: 14

Re: iMac 5k resolution not an option?

Well, for those of you taking notes back home, this didn't work (I should probably say, it didn't work for me). At least not following the guide on the Arch Wiki.
It gave me a black screen. No harm done of course since a reboot reset things back to normal.

It seems fishy that the native resolution that I get under macOS doesn't show up as default, rather the 3840x2160 that is quite OK, no visual fuzziness etc.
However, it would be nice to be able to run it the way it was meant and set everything to 200% so any further suggestions are most welcome.

Thanks.

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: iMac 5k resolution not an option?

Xrandr#Adding_undetected_resolutions

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adergaard

Member

Registered: 2016-07-27

Posts: 14

Re: iMac 5k resolution not an option?

Xrandr#Adding_undetected_resolutions

Oh yes, I saw that and followed it to the point. I may have been less than clear about that in my last post. I apologize.

For clarity, I did the following:

cvt 5120 2880

which produced the following output

# 5120x2880 59.99 Hz (CVT 14.75M9) hsync: 178.88 kHz; pclk: 1276.50 MHz
Modeline "5120x2880_60.00"  1276.50  5120 5560 6128 7136  2880 2883 2888 2982 -hsync +vsync

As per instructions on the arch wiki, I used it like so:

xrandr --newmode "5120x2880_60.00"  1276.50  5120 5560 6128 7136  2880 2883 2888 2982 -hsync +vsync

Having done that I added the new mode like so:

xrandr --addmode eDP 5120x2880_60.00     

where eDP is the name of the screen. I know when running xrandr yesterday, it said eDP-1, but today running the same command, I get eDP, see code block below (is it normal that the name changes like that?)

Screen 0: minimum 320 x 200, current 3840 x 2160, maximum 16384 x 16384
eDP connected 3840x2160+0+0 (normal left inverted right x axis y axis) 597mm x 336mm
   3840x2160     60.00*+
   ...
   ...

cutting the rest to save space

So, I finally go ahead and try it out like so:

xrandr --output eDP --mode 5120x2880_60.00

Here is where the screen goes completely black and a reboot is the only option (at least the only option I found)
--

So, any thoughts?

Last edited by adergaard (2017-02-16 19:26:17)

jasonwryan

Anarchist

From: .nz

Registered: 2009-05-09

Posts: 30,424

Website

Re: iMac 5k resolution not an option?

What is printed to the log when you change the mode and get the blackscreen? Did you try adding the sleep/safe mode option?

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seth

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Registered: 2012-09-03

Posts: 59,084

Re: iMac 5k resolution not an option?

Did you check the Xorg log on which resolutions were considered and (maybe why) disregarded?
Are you still on xf86-video-ati?

xrandr --output eDP --mode 5120x2880_60.00; sleep 20; xrandr --output eDP --mode 3840x2160

You should also be able to remote-control the box via ssh and if you're lucky, other VTs (press ctrl+alt+F1) still use a working framebuffer/resolution.

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adergaard

Member

Registered: 2016-07-27

Posts: 14

Re: iMac 5k resolution not an option?

First, let me say thanks to all who helped. It's much appreciated.
Having researched this a bit, it's a little known fact that there's no non-apple driver for the 5120x2880 mode. So Windows and Linux alike sees the screen as 3840x2160.

To moderators: While this is not "solved", you can go ahead and close it as far as I care. I'm having audio troubles now with the same installation and will start a new thread to try and pursue a solution for getting sounds to appear.

Last edited by adergaard (2017-02-17 15:03:59)

kode54

Member

Registered: 2013-10-21

Posts: 28

Re: iMac 5k resolution not an option?

I just thought I'd add to this topic: If someone feels like reverse engineering them through the totally illegitimate means of feeding them through a disassembler or decompiler, the so-called Boot Camp drivers for the AMD R9 M290X / M295X (2014) / M390 / M395 / M395X (2015) added support for the 5k resolution late last year. So while the OS does boot in 3840x2160 mode, the driver is capable of switching to the native resolution of the 5k models, using some as yet undocumented trickery.

Presumably it also has something to do with single versus multi stream protocol internally? As far as I know, the internal display uses two displayport channels to feed the 5120x2880@60 mode, otherwise it only needs a single channel for 3840x2160@60 and lower modes it happens to support.