[Troubleshooting] FreeSync + Eyefinity over HDMI?

[estebanfalso]

Hi everyone!

I apologize if maybe this is not the place to ask, but I'd really appreciate your help with the following situation: I've been planning buying a triple monitor setup, since I'm on a budget I chose the LG 24MP68VQ-P for the monitors, and would buy a RX 480 MSI Gaming X 8GB for the time being to later buy a second one.

Considering the following:

• Monitor's Input: HDMI 1.4
• Card's Output: 2xDP 1.2a, 2xHDMI 2.0b, 1xDVI-D
  

I would like to set up the monitors via Eyefinity which, to my understanding, will require an active DP - HDMI adapter -- so I can connect 2 monitors directly to the card's HDMI and use the adapter to connect the remaining one. I can't use a passive DP - HDMI adapter since the RX 480 requires at least one active connection.

My issue comes when doing some research about the FreeSync compatibility. The monitors are HDMI FreeSync compatible, that is each one of them can use FreeSync via HDMI independently. But it seems that the active DP - HDMI adapter would cause troubles and won't allow the use of FreeSync with the monitor connected to it while in Eyefinity setup.

There are some related questions on the AMD forums, dated back in August '16 and answered by the same AMD rep (TL;DR: the adapter needs to be FreeSync compatible?).

Here's where I may need to apologize for my narrow knowledge on how monitors, active adapters and cables work, but what the rep suggest doesn't seem logic to me. Given that FreeSync is basically a communication protocol to enable the sync of frames between the GPU and the display, I'm not sure I understand why would an active adapter prevent this (assuming of course that the adapter complies both with DP 1.2a and HDMI 1.4 specs, and allows for the required bandwidth and refresh frequency). For instance, using this or this active adapters. Might it be related to how the DAC works with the signal? I haven't been able to find anything related to active adapters + FreeSync.

Worst case scenario I would be able to use Eyefinity @ 75hz without FreeSync (which to me is good enough given the budget and that I'm expecting the Crossfire 480s to be able to handle the resolution nice enough).

What do you guys think?

Thanks for your answers (specially of you read the whole wall of text)!

TL;DR: Would I be able to use Eyefinity + FreeSync on a triple LG 24MP68VQ-P + RX 480 MSI Gaming X setup?

[ToastyX]

Active DP-HDMI adapters convert the signal, so the video card would be outputting a DisplayPort signal. The driver won't allow FreeSync with DisplayPort unless the adapter supports adaptive sync. Ideally you'd want to use three DisplayPort monitors for FreeSync with Eyefinity.

DVI ports can act as HDMI ports with a simple DVI-HDMI cable or adapter, so there's a chance you could just hook up all three monitors directly as HDMI. I can't find any information on whether the RX 480 actually requires an active connection beyond two monitors. I just tried setting up Eyefinity on a Sapphire Nitro+ RX 480 using the two HDMI ports and the DVI port, and it seemed to work. It recognized all three connections and extended the desktop. I don't have a way of testing FreeSync though.

[estebanfalso]

(01-18-2017 03:07 PM)ToastyX Wrote:  Active DP-HDMI adapters convert the signal, so the video card would be outputting a DisplayPort signal. The driver won't allow FreeSync with DisplayPort unless the adapter supports adaptive sync. Ideally you'd want to use three DisplayPort monitors for FreeSync with Eyefinity.

DVI ports can act as HDMI ports with a simple DVI-HDMI cable or adapter, so there's a chance you could just hook up all three monitors directly as HDMI. I can't find any information on whether the RX 480 actually requires an active connection beyond two monitors. I just tried setting up Eyefinity on a Sapphire Nitro+ RX 480 using the two HDMI ports and the DVI port, and it seemed to work. It recognized all three connections and extended the desktop. I don't have a way of testing FreeSync though.

Thanks for the explanation and for trying out the Eyefinity setup with DVI.

Regarding the passive DVI-HDMI, the only thing I could find was this Eyefinity FAQ, where the R 200 series allow for 3 passive connections, not direct confirmation with RX 400 series though.

Edit: In any case knowing that I won't need an active adapter is better, from this reply it seems that FreeSync should work over passive adapters (DP-HDMI passive is used as an example in that thread, but it shouldn't matter, right?).

[ToastyX]

FreeSync should work with both DP-HDMI and DVI-HDMI passive adapters. My only concern is the driver usually limits passive adapters to 165 MHz pixel clock, so you might not be able to get 1920x1080 @ 75 Hz without patching the driver.

[estebanfalso]

It will take me a couple of weeks to complete the setup as I will buy the 3 displays together to try them and return them if they don't work. I'll update if I was able to make it work, and if I needed to patch the driver using the Pixel Clock Patcher.

Thanks again for the help!