Samsung CHG70 FreeSync 2 Monitor Review: 32 Curved Inches Of Smooth HDR Gaming
AMD FreeSync 2 Technology Refresher
In addition to its curved screen and support for HDR, one of the Samsung CHG70's stand-out features is support for AMD FreeSync 2 technology. Although we’ve talked about FreeSync and FreeSync 2 many times in the past, we’d like to quickly go over some of the details again here. Like NVIDIA’s G-SYNC, AMD FreeSync amd FreeSync 2 keeps a display and the output from a compatible GPU in sync, regardless of frame rates or whether or not vertical sync (V-Sync) is enabled, within certain limits. For the Samsung CHG70, the range when FreeSync is enabled is 48-144Hz.
Instead of the monitor controlling the timing and refreshing at regular 60Hz intervals, which is today's most common refresh rate, the output timing control is transferred to the GPU. The GPU scans a frame out to the monitor where it is then drawn on-screen. The screen is drawn only when the frame is done rendering and the monitor doesn't update again until the next frame is done. Then, as soon as the another frame is complete, the monitor will update again as needed, in lockstep with the GPU.
To fully appreciate how adaptive refresh rate technologies like FreeSync and G-SYNC work, it’s best to experience them in person. We do have a video produced by AMD that does a good job demonstrating how FreeSync works, but it's not a replacement for actually experiencing a compatible display first-hand. We need to point out that the demo of the technology doesn’t really do it justice because the simulations and camera don’t perfectly portray all of the potential issues and fixes. To see it live and in action is to truly appreciate FreeSync, but the tech is explained in plain English in the video above, which some of you may find helpful.
As it stands today, gamers can typically choose to play their games with V-Sync (vertical sync) enabled or disabled. V-SYNC is an ancient technology that allows the output from a video source to synchronize properly with a display at a given frequency -- the most common of which is 60Hz. That may sound all well and good, but if the graphics card's output is coming at a rate above or below the vertical refresh rate of the screen, a number of issues are introduced. Disabling V-Sync may seem like the simple answer, but that causes another set of problems.
The diagram above illustrates what happens between a GPU and a display when V-Sync is enabled. In the image, the panel is refreshing at a fixed interval, but the GPU is rendering frames at different intervals. Frame 1 renders and is displayed, but Frame 2 takes a little longer, so that frame is shown on-screen twice during two monitor refresh cycles, which causes stutter during the animation and input lag when the viewer moves his mouse. And the process continues. V-Sync would be an ideal solution if the frames were rendered and output at exactly 60Hz as well, but that's not how today's games and GPUs work. It's common for games to exhibit significant variations in frame rendering and output time and it's rare that the GPU and display are actually in sync for any meaningful length of time.
Disabling V-Sync does away with the input lag, but could introduce tearing on-screen. When V-Sync is disabled, the GPU essentially pumps out frames as fast as it can, regardless of whether or not the display can actually draw them fast enough. What happens is that unfinished parts of adjacent frames are displayed on-screen, and since the positioning of the scene's elements is usually different, tear lines are introduced.
The two graphs above show how frame rates are affected when enabling / disabling V-Sync. With V-Sync enabled (red line) on a display that has a refresh rate of 60Hz, and games configured for high image quality settings to target the 40-60 FPS range, it is not uncommon to see frame rates bounce between 60 and 30 FPS for a time (half the monitor's refresh rate), which means many frames are duplicated, and that introduces lag. We should mention that this is an area where FreeSync has an advantage over G-SYNC. With FreeSync, if V-Sync is disabled, frame rates are not limited by the max refresh rate of the connected display.
When a frame is complete, it is scanned out to the screen. Frame 1 finishes in X amount of time, and it is then sent to the display. Frame 2 takes a bit longer, but when it is done, it is sent out to the screen, and so on.
FreeSync removes the fixed refresh rate limitation of most of today’s desktop displays and transfers the timing to the GPU. The screen’s refresh rate is dynamically adjusted to stay in-sync with the GPU, regardless of the frame rate, within certain limits. In doing so, FreeSync eliminates the screen tearing associated with disabling V-Sync, and minimizes the lag and stutter that come when it is enabled. We should mention that FreeSync is limited to refresh rates between 9 and 240Hz, but those limitations are beyond what any current monitor is reasonably capable of (most quality FreeSync-compatible LCDs fall within the 30Hz to 90Hz or 144Hz range, like the Samsung CHG70 we're showing you here). What FreeSync 2 adds to this display is support for HDR (High Dynamic Range) color gamut rendering, LFC, and auto-mode switching, to improve and simplify the user experience.
Instead of the monitor controlling the timing and refreshing at regular 60Hz intervals, which is today's most common refresh rate, the output timing control is transferred to the GPU. The GPU scans a frame out to the monitor where it is then drawn on-screen. The screen is drawn only when the frame is done rendering and the monitor doesn't update again until the next frame is done. Then, as soon as the another frame is complete, the monitor will update again as needed, in lockstep with the GPU.
As it stands today, gamers can typically choose to play their games with V-Sync (vertical sync) enabled or disabled. V-SYNC is an ancient technology that allows the output from a video source to synchronize properly with a display at a given frequency -- the most common of which is 60Hz. That may sound all well and good, but if the graphics card's output is coming at a rate above or below the vertical refresh rate of the screen, a number of issues are introduced. Disabling V-Sync may seem like the simple answer, but that causes another set of problems.
Disabling V-Sync does away with the input lag, but could introduce tearing on-screen. When V-Sync is disabled, the GPU essentially pumps out frames as fast as it can, regardless of whether or not the display can actually draw them fast enough. What happens is that unfinished parts of adjacent frames are displayed on-screen, and since the positioning of the scene's elements is usually different, tear lines are introduced.
Now that we’ve explained what happens when V-Sync is enabled or disabled, understanding what AMD FreeSync technology does should be simple. The slide above illustrates how frames are output to a FreeSync or FreeSynce 2 capable screen like the Samsung CHG70, when a compatible GPU is used and FreeSync is enabled in AMD’s drivers.
FreeSync removes the fixed refresh rate limitation of most of today’s desktop displays and transfers the timing to the GPU. The screen’s refresh rate is dynamically adjusted to stay in-sync with the GPU, regardless of the frame rate, within certain limits. In doing so, FreeSync eliminates the screen tearing associated with disabling V-Sync, and minimizes the lag and stutter that come when it is enabled. We should mention that FreeSync is limited to refresh rates between 9 and 240Hz, but those limitations are beyond what any current monitor is reasonably capable of (most quality FreeSync-compatible LCDs fall within the 30Hz to 90Hz or 144Hz range, like the Samsung CHG70 we're showing you here). What FreeSync 2 adds to this display is support for HDR (High Dynamic Range) color gamut rendering, LFC, and auto-mode switching, to improve and simplify the user experience.
