Another function of the eDP interface is to supply power to the screen, not just to transmit the video signal, because in the devices that have integrated it, these do not have an additional external power port.
Relationship with GPU
Internally, eDP is no different from a DisplayPort interface at all. It is when the internal wiring reaches the perimeter of the device board that its signal is transformed into an external interface, which can be an eDP connection to connect the screen of a tablet or laptop, a Classic DisplayPort output in one of its variants, a USB-C Alt-DP output and even an HDMI output if there is such a controller in between.
And here we enter a little secret, at the level of the signal generation for several screens at the same time, the part of the GPU that takes care of it has an eDP interface per supported screen, which is converted on the fly into another type to report if the device needs it. In other words, your gaming graphics card also uses an eDP interface.
What is eDP 1.5?
Normally, the eDP and Display Port standards go hand in hand, but the body in charge of creating these standards, VESA, has decided to give the umpteenth version of its on-board DisplayPort the name eDP 1.5, instead of 2.0. This comes after 6 years, since its predecessor the eDP 1.4b was released in 2015 and the new version of the standard is an incremental improvement over the previous one. Which means that it doesn’t remove anything, but rather adds improvements to what has already been done previously.
The first novelty to highlight is the author of the screen refresh, to understand it we have to imagine that our computer or our smartphone does not do anything at all and that it does not stop sending, therefore, the same picture over and over again. This means that the GPU and video RAM will be active. Well with refresh author mode we can make the screen store the last image displayed in internal memory and read its information from there while the GPU is turned off. This means great energy savings.
Another important point that we believe should be highlighted is the possibility of disconnecting sending data to the panel in times when there is no need to send the information, known as VBlank. This is crucial when we don’t have a frame buffer in the system and the picture is rendered line by line, like old TVs.
eDP 1.5, designed to save on consumption
One of the improvements that VESA added in eDP 1.5 is the so-called replay panel, which allows us to update only parts of the screen in particular while leaving the rest completely intact, for this it takes advantage also the possibility of storing in memorizing the last image displayed.
In general, the eDP 1.5 interface is designed to increase or reduce its consumption according to the level of workload to be performed. So, not only in lower resolutions and refresh rates, it will consume much less than in higher resolutions, but it will also output nothing during periods when the signal is not being sent to the screen. Highlighting in particular the inactivity between images.
Even if the screen displays nothing, the fact that the signal is active consumes a lot of energy. Temporarily disabling image delivery also involves disabling the system’s graphics hardware for this short time or reducing its clock speed.
A-SYNC for movies on eDP 1.5
Adaptive Sync is that the refresh rate and therefore the update rate of the screen is not controlled by the internal processor of the screen, but by the graphics hardware itself to which the screen is installed. screen is connected. Which, in the case of your computer, would be the graphics card. This ability was already in the previous version, but has been slightly improved in the new version.
This is a function related to video games where these tend to fluctuate unless we are playing with variable resolution, in which the FPS rate is maintained by sacrificing the amount of pixels on the screen for it. Well, in eDP 1.5 this was added for video playback to eliminate frame duplication known as stuttering and frame skipping.
For gaming panels, VESA has added new mechanisms in the new standard to reduce flicker on high frequency displays.
Linked to DisplayPort 2.0
All the new features that we have described need to be supported at the hardware level. Which translates into changes to the display driver present on the GPU, this is a video communication protocol that at the end of 2021 has yet to see a single product announced that supports eDP 1.5.
And the necessary changes must not only be made to the hardware that generates the frame and receives it, but also to the hardware that receives it to show the image that the screens themselves are. This reminds us that a lot of the DisplayPort 2.0 features are in the eDP 1.5. For example, a laptop computer with an internal eDP 1.5 interface is most likely to have DisplayPort 2.0.
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