Possibility of variable refresh rate using an AMD gpu + a 120Hz eDP 17.3" screen?

Hello everyone,
Is it possible to connect a desktop gpu such as an R9 390 to an eDP 120Hz screen such as a LP173WF2 (through an adapter board / cable) and rely on the variable timing and panel self-refresh functionality built in to current versions of eDP? But I don't know if this is done automatically between the gpu, adapter board and lcd or if something more needs to be done.

From an article:
AMD in turn fired back at NVIDIA at CES this year [2014], demonstrating their FreeSync concept, which could implement variable refresh through features found in the embedded DisplayPort (eDP) standard.

And:
According to the previous AMD FreeSync demo, any display that currently supports Variable VBLANK (like those eDP Toshiba laptops) would be compatible when using AMD GPUs and APUs.


Advice will be really appreciated.
Thanks for reading.

 

Don't bother going down this route.

Yes, technically, it's possible to find or build an adapter to connect eDP to DP. That's going to be messy, since you're going to be dealing with raw circuit boards and delicate cables lying around. Doing something like that is more of an engineering / prototyping project, and not a finished consumer product type of project. On top of that, you will need to deal with a way to mount your LCD panel.

But variable refresh rate (VRR) probably won't work. It's dependent on the panel controller chip to handle VRR. And if the panel wasn't designed with VRR from the very start, then it probably won't support VRR.

 

The LG 120Hz pannel is from 2010... I wouldn't bother as kent said as it most likely (99.99%) won't support VRR....

 

Thanks for the replies both of you.

Mounting and exposed circuitry / cables shouldn't be much of an issue. I've done projects using laptop panels and lvds driver boards before. That was the direction I was going for this as well but after reading about what eDP can do I really want to give it a go.

What about using a screen from a laptop that comes with mobile g-sync?

 

Why do you want to connect a desktop GPU to a mobile screen?

 

A portable desktop project.

 

To my knowledge, mobile Gsync laptop displays are bare displays with a particular display controller in there. There isn't a Gsync module, like there is in desktop-based Gsync monitors. And I don't think that's a good thing, because a desktop GPU will expect a monitor with a Gsync module. Otherwise, I'm sure that someone would've tried enabling Gsync on monitors without a Gsync module by now.

To be honest, I think you're chasing a white rabbit with this one. You're probably not going to find anyone that has done something like this before (connect laptop display to desktop GPU, with VRR enabled). And even attempting to explore whether it's possible will probably cost you a few hundred bucks in parts, connectors, cables, etc.

 

The reason I suggested a mobile g-sync panel is that we definitely know it supports vrr.

Your second paragraph is really where the problem lies. If I had my gpu connected to the eDP connector on the panel would I simply be able to turn on freesync? Kent1146 mentioned a panel controller chip, is this found on the panel itself?

 

PC Perspective released an article back from January 2015, that essentially "accidentally" discovered mobile Gsync. There's a follow-up article (link below) that details how nVidia gets Gsync mobile working on laptops without a Gsync module. Basically, it's relying on the mobile GPU to control the timings, and keeping very tight control of the specific display panel models being put into these specific models of laptops. I don't really think that's going to help you on the desktop side, because desktop implementations of VRR inherently need to operate through a standard protocol (Gsync or FreeSync), to handle the fact that customers in the field will be connecting a wide range of monitor make / models.
http://www.pcper.com/news/Displays/NVIDIA-G-Sync-Notebooks-Announced-No-Module-Required

I really don't think what you want to do is possible. The only way I can think of this being possible would be if you were to write a specific display driver that operated against specific timings of the exact laptop panel you had in mind.

 

So just to confirm, if I had a freesync gpu and a vrr capable display, without the correct software it's not going to work and the screen should function but with it's normal locked refresh rate.

 

Correct.

 

No special support is needed from the application. But GPU/screen/cable/driver must all match.