G-Sync and FreeSync - Clearing up some misconceptions

thank you

Hi. I've got some questions! I am shopping for a good gaming laptop and would like to know if there are any disadvantages to having a G-Sync display on a laptop? Does it have any significant impact on battery life of the laptop? Does having G-Sync display on a laptop mean that the integrated GPU is completely disabled and so all apps including non-graphics intensive ones run on the discrete GPU? Also, would using a UHD 4K display in combination with G-Sync affect battery life?

To understand the difference between FreeSync and G-Sync, you should know a little bit about Screen Tearing. https://x2.games/gsync-vs-freesync-which-is-best-for-gaming/

I've been seeing a few comparison comments lately, and some of these comments are REALLY off the mark. That said, there's some truth in some of them, so I wanted to post a compilation here. I'll amend this as new information becomes available, or as people correct me. ----------------- Contents: What is VRR? What is DisplayPort Adaptive Sync? What is G-Sync? What is FreeSync? What are the key differences? What's Next? Conclusion/TLDR ----------------- 1. What is VRR? VRR stands for Variable Refresh Rate. It's an attempt to cure two problems associated with Vsync usage; tearing and stuttering. Tearing occurs when the GPU's framebuffer and the display are out of sync (Vsync = off). Stuttering occurs when the GPU can not pump out a frame in time for the monitor's next refresh (Vsync = on). VRR allows the monitor to adjust its refresh rate on the fly to remain in sync with the GPU's framerate output, allowing for the reduction or complete removal of both tearing and stuttering under certain conditions. ----------------- 2. What is DisplayPort Adaptive Sync? DisplayPort Adaptive Sync, also know as VESA Adaptive Sync, is the OPTIONAL standard drafted by the Video Electronics Standards Association (VESA). These guys oversee some very common and royalty-free standards (like those mounting brackets for displays). VESA DisplayPort Adaptive Sync is an implementation over the DisplayPort standard beginning with DP 1.2a. It's not required for usage so DP 1.3/1.4 displays do NOT have to use this feature. In order to use this feature, the monitor must support it, the GPU must support it, and the display drivers must implement it. Currently only AMD supports it, via their branded "FreeSync," (see section #4), with Intel implementing support for the standard in the future. I want to take a moment to clear up a few misconceptions here. DisplayPort Adaptive Sync is a "basic" implementation of VRR. Aside from being a means to adjust the display's refresh rate to be in sync with the GPU's output, it doesn't do much else, like frame doubling or adjusting the response time on the fly. I'll expand more on this later. Also, while this standard is an "open standard," it is NOT open-source. It is free to implement in software (with compatible hardware), but you cannot freely download and modify the source code. ----------------- 3. What is G-Sync? G-Sync is Nvidia's implementation of VRR-based technology. In order to use G-Sync, you must have a G-Sync enabled display, a G-Sync enabled GPU, and the appropriate Nvidia driver. Currently, monitors supporting the standard must have an Nvidia G-Sync module, which carries a hefty cost but does convey some benefits over other VRR implementations. You also must have a compatible GPU. G-Sync is a proprietary standard. ----------------- 4. What is FreeSync? FreeSync is AMD's proprietary implementation of the DisplayPort Adaptive Sync standard. Contrary to some popular misconceptions, it is neither open-source nor an open-standard. While some Linux patches for FreeSync are open-source, FreeSync itself is not. Also, FreeSync requires certification through AMD (which isn't free), and an AMD provided driver in order to operate. That makes it a proprietary and closed system. FreeSync doesn't just piggyback on top of VESA Adaptive Sync, however. It adds some important features, such as LFC (Low-Framerate Compensation), as well as support for the protocol over HDMI. In terms of overall quality and features it sits in the middle, above the open standard but below G-Sync. ----------------- 5. What are the key differences? I'll try to keep this brief. G-Sync adds higher cost and lower monitor selection. However, there's a gain for this. The G-Sync module includes a custom scalar. This custom scalar not only allows the monitor to adjust its refresh rate in sync with the GPU's output, but it also adjusts the response time compensation/overdrive on the fly based on the refresh rate to minimize ghosting/overshoot as refresh rates change. It can also double frames when the framerate dips below the minimum refresh rate. Basically, a monitor rarely has a VRR range that goes below 30-40hz, as this would be perceptible to someone as "flickering." So instead, if you drop to 25fps, G-Sync doubles each frame, running at effectively 50hz. This combination of features makes G-Sync the most comprehensive VRR implementation on the market today. VESA Adaptive Sync, as mentioned above, does not do anything outside of adjust the refresh rate of the monitor to remain in sync with the GPU. And this range is affected by the quality of the scalar used. Scalars are currently provided by three companies who didn't plan for this kind of tech outside of laptop battery savings. As a result, Nvidia went in-house for their module/scalar, and the results speak for themselves. That leads us to FreeSync. The advantages to FreeSync includes implementation in a much wider range of monitors at a significantly lower cost than G-Sync. But due to the limitations of VESA Adaptive Sync and available scalars, there are some consistency issues. Many monitors have a narrow range (mine is 40-60hz). Some push the scalar too hard and flicker when near the fringes of this range. And while FreeSync has implemented a form of frame doubling (the previously mentioned LFC), it's not available on all displays. FreeSync has no current means of adjusting response time compensation on the fly like G-Sync, which is another disadvantage. ----------------- 6. What's next? Supposedly the reason that DisplayPort Adaptive Sync is optional is that Nvidia lobbied to effectively not be forced to use the same standard as AMD. I can understand that decision and further discussion of the pros/cons is outside the scope of this post. However, we are going to have a unified standard as early as Q4/2017 (though likely sometime in 2018). The HDMI Forum, the HDMI equivalent to VESA, has stated that HDMI 2.1 will REQUIRE supporting their VRR standard. if AMD and/or Nvidia want to implement HDMI 2.1 in their future GPUs, they will be required to support this VRR standard. Monitors and HDTVs supporting HDMI 2.1 will thus support VRR from both GPU providers. HDMI 2.1 may be the point where HDMI finally supplants DisplayPort in high-end gaming monitors due to its high bandwidth, feature support, and now, forced VRR compatiibliy among vendors. VESA has not yet responded by making their VRR implementation a requirement. ----------------- 7. Conclusion/TLDR VRR is currently a vendor-locked landscape where you have to go either AMD/FreeSync or Nvidia/G-Sync. Attempting to mix and match monitors and GPUs will result in no VRR support. But this will be changing with HDMI 2.1. When HDMI 2.1 displays and GPUs emerge, vendor lock-in is done. In the meantime, you have to choose between G-Sync and FreeSync. Their comparison can be summed up as this - G-Sync offers better performance and consistency, while FreeSync is available on more displays at a lower price. ----------------- Thanks for reading. I'll go through this and clear up typos and anything that needs to be re-worded in a bit.