TR has its freesync review up. There is so much difference between what TR is telling and what pcper told us about how freesync handles refresh at below the min rate of the variable refresh rate window.
http://techreport.com/review/28073/...ewed?preview=8b4bb4ec15bbabd937c955a0bff2f2ae
" Some reports have suggested that when the frame-to-frame interval on a FreeSync display grows too long, the display responds by "locking" into a 40Hz refresh rate, essentially quantizing updates at multiples of 25 ms. Doing so would be pretty poor behavior, because quantization at 25 ms steps would mean horribly janky animation. You'd be making the worst of an already bad situation where the attached PC was running up against its own performance limitations. However, such talk is kind of nonsense on the face of it, since we're dealing with a variable-refresh display working in concert with a GPU that's producing frames at an irregular rate. What happens in such cases differs between FreeSync and G-Sync, but neither solution's behavior is terribly problematic.
Let's start with how G-Sync handles it. I talked with Nvidia's Tom Petersen about this question, since he's made some public comments on this matter that I wanted to understand. Such talk is kind of nonsense on the face of it, since we're dealing with a variable-refresh display working in concert with a GPU that's producing frames at an irregular rate.
Petersen explained that sorting out the timing of a variable-refresh scheme can be daunting when the wait for a new frame from the graphics card exceeds the display's maximum wait time. The obvious thing to do is to refresh the display again with a copy of the last frame. Trouble is, the very act of painting the screen takes some time, and it's quite possible the GPU have a new frame ready while the refresh is taking place. If that happens, you have a collision, with two frames contending for the same resource.
Nvidia has built some logic into its G-Sync control module that attempts to avoid such collisions. This logic uses a moving average of the past couple of GPU frame times in order to estimate what the current GPU frame-to-frame interval is likely to be. If the estimated interval is expected to exceed the display's max refresh time, the G-Sync module will preemptively refresh the display part way through the wait, rather than letting the LCD reach the point where it must be refreshed immediately.
This preemptive refresh "recharges" the LCD panel and extends its ability to wait for the next GPU frame. If the next frame arrives in about the same time as the last one, then this "early" refresh should pay off by preventing a collision between a new frame and a gotta-have-it-now refresh.
I asked AMD's David Glen, one of the engineers behind FreeSync, about how AMD's variable-refresh scheme handles this same sort of low-FPS scenario. The basic behavior is similar to G-Sync's. If the wait for a new frame exceeds the display's tolerance, Glen said, "we show the frame again, and show it at the max rate the monitor supports." Once the screen has been painted, which presumably takes less than 6.94 ms on a 144Hz display, the monitor should be ready to accept a new frame at any time.
What FreeSync apparently lacks is G-Sync's added timing logic to avoid collisions. However, FreeSync is capable of operating with vsync disabled outside of the display's refresh range. In the event of a collision with a required refresh, Glen pointed out, FreeSync can optionally swap to a new frame in the middle of that refresh. So FreeSync is not without its own unique means of dealing with collisions. Then again, the penalty for a collision with vsync enabled should be pretty minor. (My sense is that FreeSync should just paint the screen again with the new frame as soon as the current refresh ends.)
Everything I've just explained may seem terribly complicated, but the bottom line is straightforward. FreeSync's logic for handling low-FPS situations isn't anywhere near as bad as some folks have suggested, and it isn't all that different from G-Sync's. Nvidia's method of avoiding collisions seems like it might be superior in some ways, but we're talking about small differences."
http://techreport.com/review/28073/...ewed?preview=8b4bb4ec15bbabd937c955a0bff2f2ae
" Some reports have suggested that when the frame-to-frame interval on a FreeSync display grows too long, the display responds by "locking" into a 40Hz refresh rate, essentially quantizing updates at multiples of 25 ms. Doing so would be pretty poor behavior, because quantization at 25 ms steps would mean horribly janky animation. You'd be making the worst of an already bad situation where the attached PC was running up against its own performance limitations. However, such talk is kind of nonsense on the face of it, since we're dealing with a variable-refresh display working in concert with a GPU that's producing frames at an irregular rate. What happens in such cases differs between FreeSync and G-Sync, but neither solution's behavior is terribly problematic.
Let's start with how G-Sync handles it. I talked with Nvidia's Tom Petersen about this question, since he's made some public comments on this matter that I wanted to understand. Such talk is kind of nonsense on the face of it, since we're dealing with a variable-refresh display working in concert with a GPU that's producing frames at an irregular rate.
Petersen explained that sorting out the timing of a variable-refresh scheme can be daunting when the wait for a new frame from the graphics card exceeds the display's maximum wait time. The obvious thing to do is to refresh the display again with a copy of the last frame. Trouble is, the very act of painting the screen takes some time, and it's quite possible the GPU have a new frame ready while the refresh is taking place. If that happens, you have a collision, with two frames contending for the same resource.
Nvidia has built some logic into its G-Sync control module that attempts to avoid such collisions. This logic uses a moving average of the past couple of GPU frame times in order to estimate what the current GPU frame-to-frame interval is likely to be. If the estimated interval is expected to exceed the display's max refresh time, the G-Sync module will preemptively refresh the display part way through the wait, rather than letting the LCD reach the point where it must be refreshed immediately.
This preemptive refresh "recharges" the LCD panel and extends its ability to wait for the next GPU frame. If the next frame arrives in about the same time as the last one, then this "early" refresh should pay off by preventing a collision between a new frame and a gotta-have-it-now refresh.
I asked AMD's David Glen, one of the engineers behind FreeSync, about how AMD's variable-refresh scheme handles this same sort of low-FPS scenario. The basic behavior is similar to G-Sync's. If the wait for a new frame exceeds the display's tolerance, Glen said, "we show the frame again, and show it at the max rate the monitor supports." Once the screen has been painted, which presumably takes less than 6.94 ms on a 144Hz display, the monitor should be ready to accept a new frame at any time.
What FreeSync apparently lacks is G-Sync's added timing logic to avoid collisions. However, FreeSync is capable of operating with vsync disabled outside of the display's refresh range. In the event of a collision with a required refresh, Glen pointed out, FreeSync can optionally swap to a new frame in the middle of that refresh. So FreeSync is not without its own unique means of dealing with collisions. Then again, the penalty for a collision with vsync enabled should be pretty minor. (My sense is that FreeSync should just paint the screen again with the new frame as soon as the current refresh ends.)
Everything I've just explained may seem terribly complicated, but the bottom line is straightforward. FreeSync's logic for handling low-FPS situations isn't anywhere near as bad as some folks have suggested, and it isn't all that different from G-Sync's. Nvidia's method of avoiding collisions seems like it might be superior in some ways, but we're talking about small differences."