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dufeu
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PostPosted: Wed Nov 09, 2016 11:29 pm    Post subject: Experiences regarding paired 4K screens [Informed Gotchas] Reply with quote

I'm seriously considering swapping out my 3 head HD 1920x1080p monitors for a pair of UHD 3840x2160 monitors.

I have a Gigabyte GA-F2A88X-UP4 (FM2+) motherboard paired with a AMD A10-7850K APU. According to Gigabyte:
Quote:
1 x HDMI port, supporting a maximum resolution of 4096x2160
* The resolution of 4096x2160 can be supported when using an FM2+ APU; the maximum resolution supported is 1920x1200 when using an FM2 APU.
* Support for HDMI 1.4a version.
1 x DisplayPort, supporting a maximum resolution of 4096x2160
* The DisplayPort does not support Hot plug. If you want to change to another graphics port when the computer is on, be sure to turn off the computer first.
* Support for DisplayPort 1.2 version.

Does anyone have experience with this type of configuration (FM2+ MB with AMD APU)? Are there any "gotchas"?

Even on sale (Black Friday), the new 32" monitors are not exactly cheap and I'd really like to know if other people have had success doing this. I'm not a gamer but I do play back and work with video (subtitling work) a fair amount.

A single monitor would still give me a 'larger' desktop area but two would be utter bliss.
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Last edited by dufeu on Fri Dec 23, 2016 12:18 am; edited 2 times in total
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Ant P.
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PostPosted: Thu Nov 10, 2016 4:38 am    Post subject: Reply with quote

I'm only going off what I've learned from studying Mesa docs but: on AMD parts, DisplayPort outputs are independent of others and get dedicated resources (which wasn't the case with older connectors), so you shouldn't have GPU issues with multiple 4K screens.

The part you'll need to pay attention to is the bandwidth. For that workload the memory should be able to keep up, but each output will be transmitting 15Gbit/s; monitor cables can fail just like network cables at these speeds, quality and length really starts to matter.
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dufeu
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PostPosted: Fri Nov 11, 2016 3:44 am    Post subject: Reply with quote

Ant P. wrote:
The part you'll need to pay attention to is the bandwidth. For that workload the memory should be able to keep up, but each output will be transmitting 15Gbit/s; monitor cables can fail just like network cables at these speeds, quality and length really starts to matter.

Actually, it turns out the bandwidth is the key issue.

The spec for HDMI 1.4(a)(b)supports 3840x2160 up to 30Hz refresh rate. This translates to a maximum video transfer rate of 3.4 Gbps. At 3840x2160 resolution, the DP 1.2 spec supports a maximum video transfer rate of 17.28 Gbps which enables a refresh rate as high as 75Hz. In other words, you need at least 1 HDMI 2.0 port paired with a DP 1.2 port (or equivalent) to run paired 4K monitors with a 60Hz refresh rate. It also implies the computer itself should be new enough to have paired PCIE 3.0 slots for dual graphics cards for best results.

I could probably run a pair of 4K monitors, but I'm not sure I really want to run one monitor at 60 Hz side by side with the second at 30 Hz. I suspect that would most likely result in literal headaches. Also, I imagine 60fps video wouldn't display properly either.

I am getting a single 4K monitor though. I intend to experiment with retaining at least one of the 1920x1080 monitors and possibly two of them. Since I already run a 3 head setup, this should easily be within the capability of my current hardware.

I'll update this once the new monitor arrives. I hope to be able to set up my movies on one of the 1080p screens and retain the 4K monitor primarily for desktop real estate. ;)
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thumper
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PostPosted: Wed Nov 16, 2016 10:19 pm    Post subject: Reply with quote

Here is a similar topic you may want to check out.
https://forums.gentoo.org/viewtopic-t-1042444-highlight-.html

George
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dufeu
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PostPosted: Fri Dec 23, 2016 12:16 am    Post subject: Reply with quote

thumper wrote:
Here is a similar topic you may want to check out.
https://forums.gentoo.org/viewtopic-t-1042444-highlight-.html

George

Thanks for the tip! It is a relevant thread.

I'm including my experiences/findings here as well as adding a separate (differing content) comment there.

I ended up purchasing 2 4K monitor/tv Black Friday loss leaders as they were less than $800 including shipping together.

  • 32" QNIX model UHD3216 Real 4K MINE
  • 49" LG UHD TV 4K model [LG] webOS UHD6030

Long story short, I'm having no problem running both monitors in 4K mode as a dual head system. If you want to know the specifics and 'gotchas', read on.

Like all variable monitors, these are 'backwards compatible'. If your graphics ports will only output 2560x1600, they will display 2560x1600. The point here is not to get hung up on whether you have DisplayPort 1.2 or DisplayPort 1.4 or HDMI 1.4 or HDMI 2.0. In order to display 4K (UHD) resolution your graphics ports must meet certain minimum levels. You do need to match up your available graphics ports/capabilities to the ports available on the monitors.

For 4K resolution, your must have at least DisplayPort 1.2 or HDMI 1.4b capability. Later versions will enable certain 4k features but 4k resolution requires these minimums. The defining standard for Dual DVI is limited to a maximum resolution of 2560x1600. Therefore, no Dual DVI graphics port will drive a UHD TV/monitor in 4k mode.

My motherboard has an FM2+ socket with an AMD APU type processor. It's set up with three graphics ports with built-in support for 3 monitors. These ports are 1 DP 1.2, 1 HDMI 1.4b and 1 Dual DVI. According to the specs on Gigabyte's site for this motherboard, I can run all three graphics ports simultaneously. I have 32GB RAM installed and I've dedicated 2GB (the max possible) for graphics.

The DP and HDMI ports are both capable of driving 4096x2160 displays. At 4096x2160 resolution, the DP port has a maximum refresh rate of 60Hz while the HDMI port has a maximum refresh rate of 24hz. At 3840x2160 (UHD) resolution, these maximum refresh rates change to 61Hz and 30Hz respectively.

The QNIX monitor comes with DP 1.4 and HDMI 2.0 ports. The LG UHD TV/monitor comes with 1 HDMI 2.0 ports and 2 HDMI 1.4 ports. The LG UHD6030 is advertised as capable of a 120Hz refresh rate. Both monitors are considered good to excellent for gamers. i.e. I'm 'future proofed' if I choose to upgrade my graphics hardware.

Since my graphics ports are one generation back, I'm limited to the minimum refresh rates. Since I'm not a gamer, this isn't a problem for me.

It turns out that while LG advertises the UHD6030 as a UHD TV, it's actually capable of 4096x2160 resolution.

Real Life Experience/Notes/Gotchas:

Having lived with these monitors for 4 weeks now, there are some definite pointers/gotchas I'd like to share:
  1. It doesn't make sense to get anything less 32" if you're getting a UHD monitor. The pixels will be so small that you'll have to increase your system font sizes to be able to read anything assuming the monitor is more than two feet from your eyes. Really.

  2. Buy mounting arms. Don't even speculate about putting them directly on whatever you use for a desk. For the 49" LG, I bought a wall mount type arm. My equipment rack is directly behind my desk. Since it's very sturdy, counter-balanced and on an anti-tipping floor plate, I had no problem putting the mounting arm on the equipment rack. I think the 49" LG actually weighs slightly less than the 32" QNIX. I got a desk mount arm for the 32" QNIX. The arms work great and make managing my work surface/physical space a lot more sensible.

  3. It seems all the UHD TV/Monitors now come with remotes. Gotcha! The ON/OFF button on both remotes works on both monitors. The menu buttons also effect both monitors but in different ways. You have to be really careful where you hold and point the remote in order to not affect the monitor you're not changing settings for. There is no facility to explicitly and exclusively pair a remote with it's associated TV/Monitor. This is really thoughtless on the part of the manufacturers. Recently, I installed strings of multi-color LED party lights on a patio. I could explicitly pair each string of lights with a different remote. Pairing was as simple as holding down the power button on the remote while turning on the string I wanted that remote to control. The same was true for the installation of remotes in 4 overhead fans on the same patio. This isn't rocket science here. There are plenty of situations where multiple TVs/Monitors are installed. Go figure. Or go to just about any bar or doctor's office these days.

  4. Both monitors are this year (2016) releases. Gotcha! You must be running the latest versions of X11, the appropriate graphics drivers, kernel and windows manager. Prior version of any of these may not deal with the EDID information returned by the monitors correctly.

    1. The QNIX monitor is strictly UHD (3840x2160) resolution. When I originally hooked it up, KDE Settings reported 60Hz and 30Hz available refresh rates. Gotcha! While the QNIX monitor will run at 30Hz with no problem, it will display nothing at 60Hz. After a set of global updates, KDE settings now reports available refresh rates of 61Hz and 30Hz. The monitor runs perfectly fine at the faster 61Hz rate.

    2. Gotcha! Yep. A related gotcha. For the QNIX at 61Hz, you must use a DP 1.4 certified cable. Earlier cables will not work. There's no actual 'certification levels' for DP or HDMI cables. Instead, you need to check the guaranteed data rate specification in any DP or HDMI cable you want to buy. If no guaranteed data rate specification is listed, assume it's for older DP/HDMI ports and don't bother getting it.

    3. The LG monitor presents different EDID problems. Gotcha! As a TV/Monitor, LG assumes a lot. First, that your primary use is as a TV. This means they want a connection to the Internet. The default installation process is heavily TV settings based. Be prepared to 'skip' a lot of 'features'.

    4. The LG will respond to the screen hibernation mode command as sent by your computer. The screen will go off. Gotcha! But, after the screen is off {less than 1 minute}, it goes into it's own built-in screen saver mode telling you there are no active inputs. Here is the kicker, after doing slideshow screen saver for several minutes, it powers off and goes into deep hibernation mode. After some period of time I've not yet determined, it goes into really deep hibernation mode. This mode is deep enough to signal your computer that the monitor is no longer connected. Most of the window managers I use will respond in one way or another to having a monitor disconnected in a multi-head setup. With KDE, all the windows are squashed over on one side of the screen. I haven't yet found any settings in the LG which will let me control this. In theory, there is a setting to turn off the automatic screen saver, but that doesn't apply in this situation. {Sarcasm} Thank you LG for knowing what we need/want better than we do.

  5. So long as it's not in full screen mode, I have no problems playing any of my videos on the QNIX monitor. The same is true with the LG monitor with the exception of a few videos I have which are 60 fps. At full screen mode, I get visible tearing with both monitors. The tearing isn't all the time but is more significant and obvious in medium to high action sequences. This is most likely due to limitations inherent in my hardware. A better GPU arrangement with more GPU memory would probably reduce the tearing issue at full screen but opening a window up to cover about 90% of the screen works well with almost no tearing. Works for me. Note: for obvious reasons, the tearing on the LG (24Hz) is worse than on the QNIX (61Hz)

  6. I'd also like to note that opening a 1920x1080 {HD} window for video playback on the LG monitor {49"} results in a physical display of the same size as playing back said video on one of my 1920x1080 {24"} monitors. In other words, being able to play videos at 90% of screen size without tearing in these larger monitors is still a huge step up. While it would be nice to have a better GPU setup, I'm not hurting.

  7. added 12/26/2016 - I just finally realized another Gotcha!. I've been have sporadic graphics related 'freezes' since swapping out my 3-head HD setup for this 2-head UHD setup. Basically, I'm driving the equivalent of an 8-head HD setup. I didn't sufficiently appreciate how much {almost 3X as much} more work my 8 graphics compute units would be called upon to do. For now, I turned off 'turbo boost' and I set the clock multiplier down from 37 to 35 (3.7GHz to 3.5GHz. I'm definitely going to need a better CPU cooler. Turning off turbo boost and cutting down the clock multipler 2 notches resulted in a 25 C drop.

  8. For reference, these are my current version levels of mentioned packages software:
    Code:
    [I] x11-base/xorg-server
         Installed versions:  1.18.4{tbz2}(12:37:53 PM 12/19/2016)(glamor ipv6 suid udev xorg -dmx -doc -kdrive -libressl -minimal -selinux -static-libs -systemd -tslib -unwind -wayland -xephyr -xnest -xvfb)

    Code:
    [I] media-libs/mesa
         Installed versions:  13.0.2^d{tbz2}(11:46:23 PM 12/14/2016)(classic dri3 egl gallium gbm gles2 llvm nettle nptl opencl vaapi vdpau wayland xvmc -bindist -d3d9 -debug -gcrypt -gles1 -libressl -openmax -openssl -osmesa -pax_kernel -pic -selinux -valgrind -vulkan -xa ABI_MIPS="-n32 -n64 -o32" ABI_PPC="-32 -64" ABI_S390="-32 -64" ABI_X86="32 64 -x32" KERNEL="-FreeBSD" VIDEO_CARDS="r600 radeon radeonsi -freedreno -i915 -i965 -ilo -intel -nouveau -r100 -r200 -r300 -vc4 -vmware")

    Code:
    [I] kde-apps/kde-meta
         Installed versions:  16.12.0(5){tbz2}(08:48:55 AM 12/20/2016)

    Code:
    [I] x11-drivers/xf86-video-amdgpu
         Installed versions:  9999{tbz2}(12:38:36 PM 12/19/2016)(glamor)

    Code:
    Linux pyrogyro 4.8.15-gentoo #1 SMP PREEMPT Mon Dec 19 11:57:16 EST 2016 x86_64 AMD A10-7850K Radeon R7, 12 Compute Cores 4C+8G AuthenticAMD GNU/Linux


I really, really, really like having a 7936x2160 desktop. That's larger than having 8 1920x1080 monitors.
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