Take a look at this photo. See that horizontal break halfway down?1 That break is called a “screen tear.” You’d never tolerate it in your still photographs, but screen tears are a constant torment for PC gamers. They come and go in a flash, but that’s enough to annoy.
Vertical synchronization, or v-sync, is the traditional solution to screen tearing, but it introduces its own problems. Project FreeSync helps solve tearing without those problems or the use of proprietary technology. Project FreeSync what gamers have been waiting for, but its benefits go beyond gaming.
MEET PROJECT FREESYNC
Computer monitors are refreshed at a constant rate, usually 60 times per second. On the other hand, game framerates are sporadic: the computer draws frames as fast as it can, and that varies constantly. Meanwhile, normal video content plays back at a steady rate, usually 23.976 frames per second.
As you can see, your content and your monitor are never in complete sync. That’s what causes the screen to "tear:" the monitor is being fed a new frame before it’s finished drawing the last one. For a variety of reasons, games are the worst offender.
Traditionally, we solve the gaming problem with vertical synchronization, or v-sync. When v-sync is on, the computer lets the monitor set the pace. The PC delivers frames only at intervals that fit the monitor’s refresh rate exactly; the content and monitor are now synced and the tears are gone.
But there’s a catch: when the game action picks up and your PC's framerate dips, the monitor may not receive a new frame from the GPU in time for its next refresh, so the monitor displays the current frame a second time. Where you might have had a tear in the picture with a higher framerate, now you have stuttering or lag. It's a short lag, but it's obvious and intolerable to many gamers. There are even ways to alleviate the stuttering with v-sync, but these methods introduce "input lag," or a delay between the time the player moves the mouse and the movement appears on-screen. These scenarios demonstrate a traditional wisdom that every attempt to fix the basic problem of "tearing" introduces problems of its own.
But there is a solution that upends traditional wisdom: allow the monitor's refresh rate to vary (e.g. 9-60 times per second), and let that refresh rate be controlled by and synchronized to the graphics card. That very ability was proposed by AMD to VESA, the standards body that oversees the DisplayPort specification. Our proposal was accepted and integrated into the DisplayPort 1.2a specification as a feature going by the name of "DisplayPort Adaptive-Sync."
Thanks to AMD's help, monitors that support the DisplayPort Adaptive-Sync specification—and there will be a lot of them—will feature dynamic refresh rates. To actually utilize the features of such a monitor, however, you need a graphics card and a graphics driver that can leverage the Adaptive-Sync feature to manage how the content and monitor are synchronized.
Project FreeSync is AMD's name for the complete solution: a compatible AMD Radeon™ graphics card, an enabled AMD Catalyst™ graphics driver, and an Adaptive-Sync-aware display. Together, these three pieces will abolish tearing, eliminate stuttering, and greatly reduce input latency.
Jay Lebo is a Product Marketing Manager at AMD. His postings are his own opinions and may not represent AMD’s positions, strategies or opinions. Links to third party sites are provided for convenience and unless explicitly stated, AMD is not responsible for the contents of such linked sites and no endorsement is implied.
1. This image is a simulation.
*Originally posted by Robert Hallock in AMD Gaming on May 29, 2014 5:03:00 PM