AMD’s Freesync 2 changes the display game

Three major improvements with more to come

rtg-logo Radeon AMD logoAMD’s Freesync 2 is going to fundamentally change the way monitors work for the better. There are three main things it does but SemiAccurate thinks one, communications, is the killer app.

The three main pillars of Freesync 2 are HDR tone mapping, LFC (Low Framerate Compensation), and low latency. Some of these are related but they all have direct beneficial impacts on the user, you will see the difference. Better yet this whole slew of advances tends to simplify the monitors potentially making for cheaper devices once volume comes up. There really isn’t a down side to all of this.

Lets start out with HDR tone mapping, potentially one of the most important new technologies since digital displays. You might recall in the early days of flat panel monitors VGA was the signal transport of choice. It was analog and you had the brilliant chain of a digital signal getting converted to analog for the cable, then back to digital for the display. Pixels crawled, colors bled, and in general anything but the native rez of the panel was unusable. DVI-D fixed all of this but we face a similar headache with HDR.

The idea is as simple as it is stupid, an artifact of too much design by committee. With HDR and to a lesser extent any monitor out there, you have the game engine rendering the scene for each frame. It then tone maps to the correct colors and fires it off to the display drivers. This tone mapping may or may not be correct for the monitor, it could render in more or less colors than the monitor can display. The driver has to adjust for some of this and the display has to re-tone map for the correct output. If the engine renders too many colors, things generally work out OK, too few and you get less colors than you can display. In general it is an imperfect system that tends to result in crappy display results.

AMD Freesync 2 HDR tone mapping

Before and after Freesync 2

Step up to Freesync 2 and the aforementioned communications. The big change is with FS2 a monitor can signal the driver and more importantly the OS and game engine to its output capabilities. The game engine can now render the scene to exactly the monitor’s capabilities instead of a guess that is almost always wrong. This simple idea sounds obvious and it is, but until now the monitors had no way of telling the host device what their capabilities were so there was no way to implement the change. Now you can so expect this ‘minor’ change in connectivity to be used in other ways once it becomes widespread.

Tone mapping may sound like the killer app but the real one is lowering latency. If you notice the above way had at least three steps where the entire image was twiddled for color depth and other things. This takes compute power, energy, and most importantly time. Cheaper devices will come about when these twiddlings don’t need to happen any more, and it will save energy and reduce heat too. Add in mandatory 2x sRGB brightness and color for FS2 certification and you have even more work to do per frame. Best of all it takes a huge whack out of latency, those twiddlings took a lot of time and now they aren’t in the pipe.

This may not sound important either unless you game a lot but if you use VR, it will matter and matter a lot. Display latency like this was a large part of lag and the queasy effects it brought on and there was nothing a developer could do about this portion. With Freesync 2 it is gone, poof. If VR headsets don’t adopt FS2 in very short order, I will be surprised, it will be a major step in the user experience for less cost than the old way.

The last major bullet point is LFC or low frame rate compensation, one of the major pain points of AMD GPUs lately. The problem is that when frame rates drop very low, below what a monitor can display, you get all sorts of artifacts that cause stuttering, tearing, and a general crappy user experience. With Freesync 2 LFC is mandatory so all those problems go away, or at least are far less annoying to the user. This is a proverbial good thing and AMD is doing right by making it mandatory. While some others *cough* Intel *cough* make anti-user but margin boosting things mandatory, AMD does exactly the opposite.

There are a few other things in Freesync 2 like automatic mode switching to compensate for OSes that are dumber than their users, but since we scoff at Windows we won’t go much further than that. The short version is that Windows is pretty broken on HDR monitors and Microsoft cares enough about their userbase to spend their time and money on forced march upgrades rather than basic usability fixes. AMD seems to be compensating for this behavior with Freesync 2.

In the end Freesync 2 will be everywhere, the benefits are too great for the ecosystem to not adopt it. The changes will result in cheaper, more efficient, and lower latency panels but it will take time for the changes to be widespread enough for OEM/ODMs to pull legacy cruft. Best of all is the updated communications paths, they underpin most of the changes, are simple enough to implement, and will lead to a lot of interesting hacks in the near future. Freesync 2 can’t come soon enough.S|A

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Charlie Demerjian

Roving engine of chaos and snide remarks at SemiAccurate
Charlie Demerjian is the founder of Stone Arch Networking Services and SemiAccurate.com. SemiAccurate.com is a technology news site; addressing hardware design, software selection, customization, securing and maintenance, with over one million views per month. He is a technologist and analyst specializing in semiconductors, system and network architecture. As head writer of SemiAccurate.com, he regularly advises writers, analysts, and industry executives on technical matters and long lead industry trends. Charlie is also a council member with Gerson Lehman Group. FullyAccurate