Is it not based in VESA Adaptive Sync used in DisplayPort? That is why it seems to be more designed to DP.
Edit - Found it.
https://www.amd.com/en/technologies/free-sync-faq#faq-What-is-DisplayPort-Adaptive-Sync-and-how-does-it-differ-from-AMD-FreeSync™-technology?
That is why it feels a lot like designed to DisplayPort... FreeSync uses the VESA Adaptive Sync protocol to communicate.
Almost right. DP 1.0 had a rudimentary method of adjusting the refresh rate based on the needs of laptop devices to conserve power. Lower screen refresh meant a potential savings in energy used by the display. It wasn't really suited for gaming or quickly varying the refresh rate constantly.
AMD used that as the basis to create FreeSync making modifications to make it suitable for use cases (like gaming) requiring frequent quick changes in refresh frequency in order to sync the display to the graphics output of a GPU. AMD then took those changes and made a proposal to the VESA standards body to incorporate those changes into a VESA standard that became VESA Adaptive Sync.
Basically AMD didn't use VESA Adaptive Sync because it didn't exist until a few years after AMD created FreeSync and then AMD made the proposal to the VESA Standards body.
It's more correct to say that VESA Adaptive Sync uses FreeSync since it's basically a form of FreeSync.
Since AMD wasn't collecting royalties for FreeSync some TV controller chipmakers with assistance by AMD built in support for FreeSync into their controller chips. Hence you had support for VRR via FreeSync over HDMI on HDMI TVs like LG, Samsung and other 2nd tier Korean display makers like Wasabi Mango and others. This started with HDMI 1.2. There are a LOT of HDMI 1.2 - 2.0+ TVs that use those controller chips but don't have FreeSync/VESA Adaptive Sync exposed to the user since they also require firmware support and most TV makers didn't bother to either enable it in the basic firmware that the chipmakers provide or don't choose to incorporate into the custom firmware that they create for their particular TV.
Eventually the HDMI group finally got around to releasing their version of VRR in HDMI 2.1 using VESA Adaptive Sync as a basis, but obviously with quite a few changes.
All of that was different from say NV who designed something from the ground up to provide variable refresh rate. They didn't want to use what was available on laptops (like what is in DP 1.0) because of 2 reasons. First, it wasn't suitable to gaming requirements. Second, they wanted full control so that they could monetize it and collect royalties from display makers who utilized their VRR implementation (which would come to be known as Gsync). Because of that, display makers who wanted to have Gsync on their displays had to purchase a Gsync module to be used in the manufacture of the display. To its credit that hardware module provided more capabilities than AMD's freely available FreeSync (which also came out later than Gsync).
However, since FreeSync/VESA Adaptive Sync (basically the same thing) is freely available with no royalties attached and it's "good enough" it has seen far wider adoption than Gsync (at one point the hardware modules for Gsync were 150 USD, no idea how much they are now). When NV finally broke down and supported VESA Adaptive Sync, they just labeled it as another form of Gsync on their end.
And while not "officially supported" it obviously also works with FreeSync monitors that were available long before VESA adopted AMD's FreeSync (VESA Adaptive Sync).
Regards,
SB
