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Nvidia explains what is Fast Sync? This new technology is a new Sync technology, different from G-Sync. It's implemented in the GPU as a buffer. Watch for details.
This video was recorded at U.S.A. Texas Austin Nvidia Global Presentation of GeForce GTX 1080 and GTX 1070. After the agreed NDA date we are making the record publicly available for all technology enthusiasts. There are great many details about new Nvidia Pascal architecture, new 16 nanometer production process, new drivers, software features and VR (Virtual Reality) in this series.
Nvidia GeForce GTX 1080 Review: NVIDIA GeForce GTX 1080 İncelemesi - Technopat (Turkish language)
Fast Sync is a latency-conscious alternative to traditional Vertical Sync (V-SYNC) that eliminates tearing, while allowing the GPU to render unrestrained by the refresh rate to reduce input latency.
Rendered Frames - Traditional Method
This is a rough outline of how frame rendering works through the NVIDIA graphics pipeline:
The game engine is responsible for generating the frames that are sent to DirectX. The game engine also calculates animation time; the encoding inside the frame that eventually gets rendered. The draw calls and information are communicated forward, the NVIDIA driver and GPU converts them into actual rendering, and then spits out a rendered frame to the GPU frame buffer. The last step is to scan the frame to the display.
We are doing something different now with Pascal.
High FPS Games
High FPS games like Counter-Strike: Global Offensive are running at many hundreds of frames per second today on Pascal. The question is: what good is that? Today, there are two choices on how to display the game; with V-SYNC ON or with V-SYNC OFF.
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If you use V-SYNC ON, the pipeline gets back-pressured all the way to the game engine, and the entire pipeline slows down to the refresh rate of the display. With V-SYNC ON, the display is essentially telling the game engine to slow down, because only one frame can be effectively generated for every display refresh interval. The upside of V-SYNC ON is the elimination of frame tearing, but the downside is high input latency.
When using V-SYNC OFF, the pipeline is told to ignore the display refresh rate, and to deliver game frames as fast as possible. The upside of V-SYNC OFF is low input latency (as there is no backpressure), but the downside is frame tearing.
These are the choices that gamers face today, and the vast majority of eSports gamers are playing with V-SYNC OFF to leverage its lower input latencies, lending them a competitive edge. Unfortunately, tearing at high FPS causes a vast amount of jittering, which can hamper their gameplay.
Decoupled Render and Display
NVIDIA has taken another look at how the traditional process works, and for the first time, rendering and display are being decoupled from the pipeline. This allows the rendering stage to continually generate new frames from data sent by the game engine and driver at full speed, and those frames can can be temporarily stored in the GPU frame buffer.
Rendered Frames - FAST SYNC
NVIDIA has decoupled the front end of the render pipeline from the backend display hardware. This allows different ways to manipulate the display that can deliver new benefits to gamers. Fast Sync is one of the first applications of this new approach.
With Fast Sync, there is no flow control. The game engine works as if V-SYNC is OFF. And because there is no backpressure, input latency is almost as low as with V-SYNC OFF. Best of all, there is no tearing because FAST SYNC chooses which of the rendered frames to scan to the display. FAST SYNC allows the front of the pipeline to run as fast as it can, and it determines which frames to scan out to the display, while simultaneously preserving entire frames so they are displayed without tearing.
[TBODY]
[/TBODY]
The experience that FAST SYNC delivers, depending on frame rate, is roughly equal to the clarity of V-SYNC ON combined with the low latency of V-SYNC OFF.
Decoupled Buffers
One way to think about Fast Sync is to imagine that three areas in the frame buffer have been allocated in three different ways. The first two buffers are very similar to double-buffered VSYNC in classic GPU pipelines. The Front Buffer (FB) is the buffer scanned out to the display. It is a fully rendered surface. The Back Buffer (BB) is the buffer that is currently being rendered to
and it can’t be scanned out until it is completed. Using traditional VSYNC In high render-rate games is not good for latency, since the game must wait for the display refresh interval to flip the back buffer to become the front buffer before another frame can be rendered into the back buffer. This slows down the entire process…and adding additional back buffers just adds latency, since they could all fill up at high rendering rates, causing similar stalls of the game engine.
Fast Sync introduces a third buffer called the Last Rendered Buffer(LRB) which is used to hold all newly rendered frames just completed in the back buffer – in effect having a copy of the most recently rendered back buffer - until the front buffer has finished scanning, at which point the Last Rendered Buffer is copied to the Front buffer and the process continues. Actual buffer copies would be inefficient, so instead the buffers are just renamed. The buffer being scanned to the display is the FB, the buffer being actively rendered to is the BB and the buffer holding the most recently rendered frame is the LRB. New flip logic in the Pascal architecture controls the entire process.
A typical process would look like this:
FAST SYNC Latency Results
The data is compelling. Latency is high with V-SYNC ON. Gamers of high FPS games today use V-SYNC OFF to get the best input response in their games, while dealing with the jitter caused by tearing at high frame rates. Turning FAST SYNC on delivers ~8ms more latency than V-SYNC OFF, while delivering entire frames without issues like tearing and jitter.
These samples were taken with a high-speed camera using Counter-Strike: Global Offensive.
NOTE Fast Sync is best tested with high FPS DX9 games.
NVIDIA Control Panel
FAST SYNC settings can be set in the NVIDIA Control Panel in the Manage 3D settings section under the Vertical sync setting.
NOTE: The default setting for Vertical Sync is to use the 3D application setting.
This video was recorded at U.S.A. Texas Austin Nvidia Global Presentation of GeForce GTX 1080 and GTX 1070. After the agreed NDA date we are making the record publicly available for all technology enthusiasts. There are great many details about new Nvidia Pascal architecture, new 16 nanometer production process, new drivers, software features and VR (Virtual Reality) in this series.
Nvidia GeForce GTX 1080 Review: NVIDIA GeForce GTX 1080 İncelemesi - Technopat (Turkish language)
Fast Sync is a latency-conscious alternative to traditional Vertical Sync (V-SYNC) that eliminates tearing, while allowing the GPU to render unrestrained by the refresh rate to reduce input latency.
Rendered Frames - Traditional Method
This is a rough outline of how frame rendering works through the NVIDIA graphics pipeline:
The game engine is responsible for generating the frames that are sent to DirectX. The game engine also calculates animation time; the encoding inside the frame that eventually gets rendered. The draw calls and information are communicated forward, the NVIDIA driver and GPU converts them into actual rendering, and then spits out a rendered frame to the GPU frame buffer. The last step is to scan the frame to the display.
We are doing something different now with Pascal.
High FPS Games
High FPS games like Counter-Strike: Global Offensive are running at many hundreds of frames per second today on Pascal. The question is: what good is that? Today, there are two choices on how to display the game; with V-SYNC ON or with V-SYNC OFF.
| V-SYNC | ON | OFF |
| Flow Control | Backpressure | None |
| Input Latency | High | Low |
| Frame Tearing | None | Tearing |
If you use V-SYNC ON, the pipeline gets back-pressured all the way to the game engine, and the entire pipeline slows down to the refresh rate of the display. With V-SYNC ON, the display is essentially telling the game engine to slow down, because only one frame can be effectively generated for every display refresh interval. The upside of V-SYNC ON is the elimination of frame tearing, but the downside is high input latency.
When using V-SYNC OFF, the pipeline is told to ignore the display refresh rate, and to deliver game frames as fast as possible. The upside of V-SYNC OFF is low input latency (as there is no backpressure), but the downside is frame tearing.
These are the choices that gamers face today, and the vast majority of eSports gamers are playing with V-SYNC OFF to leverage its lower input latencies, lending them a competitive edge. Unfortunately, tearing at high FPS causes a vast amount of jittering, which can hamper their gameplay.
Decoupled Render and Display
NVIDIA has taken another look at how the traditional process works, and for the first time, rendering and display are being decoupled from the pipeline. This allows the rendering stage to continually generate new frames from data sent by the game engine and driver at full speed, and those frames can can be temporarily stored in the GPU frame buffer.
Rendered Frames - FAST SYNC
NVIDIA has decoupled the front end of the render pipeline from the backend display hardware. This allows different ways to manipulate the display that can deliver new benefits to gamers. Fast Sync is one of the first applications of this new approach.
With Fast Sync, there is no flow control. The game engine works as if V-SYNC is OFF. And because there is no backpressure, input latency is almost as low as with V-SYNC OFF. Best of all, there is no tearing because FAST SYNC chooses which of the rendered frames to scan to the display. FAST SYNC allows the front of the pipeline to run as fast as it can, and it determines which frames to scan out to the display, while simultaneously preserving entire frames so they are displayed without tearing.
V-SYNC ON | V-SYNC OFF | FAST SYNC | |
Flow Control | Backpressure | None | None |
Input Latency | High | Low | Low |
Frame Tearing | None | Tearing | None |
The experience that FAST SYNC delivers, depending on frame rate, is roughly equal to the clarity of V-SYNC ON combined with the low latency of V-SYNC OFF.
Decoupled Buffers
One way to think about Fast Sync is to imagine that three areas in the frame buffer have been allocated in three different ways. The first two buffers are very similar to double-buffered VSYNC in classic GPU pipelines. The Front Buffer (FB) is the buffer scanned out to the display. It is a fully rendered surface. The Back Buffer (BB) is the buffer that is currently being rendered to
and it can’t be scanned out until it is completed. Using traditional VSYNC In high render-rate games is not good for latency, since the game must wait for the display refresh interval to flip the back buffer to become the front buffer before another frame can be rendered into the back buffer. This slows down the entire process…and adding additional back buffers just adds latency, since they could all fill up at high rendering rates, causing similar stalls of the game engine.
Fast Sync introduces a third buffer called the Last Rendered Buffer(LRB) which is used to hold all newly rendered frames just completed in the back buffer – in effect having a copy of the most recently rendered back buffer - until the front buffer has finished scanning, at which point the Last Rendered Buffer is copied to the Front buffer and the process continues. Actual buffer copies would be inefficient, so instead the buffers are just renamed. The buffer being scanned to the display is the FB, the buffer being actively rendered to is the BB and the buffer holding the most recently rendered frame is the LRB. New flip logic in the Pascal architecture controls the entire process.
A typical process would look like this:
- Scan from FB
- Render to BB
- When Render completes
- BB becomes LRB
- LRB becomes BB and render continues
- When Render completes
- BB becomes LRB
- LRB becomes BB and render continues
- When Render completes
- BB becomes LRB
- LRB becomes BB and render continues
- When scan completes
- LRB becomes FB
- Start scanning from the new FB
FAST SYNC Latency Results
The data is compelling. Latency is high with V-SYNC ON. Gamers of high FPS games today use V-SYNC OFF to get the best input response in their games, while dealing with the jitter caused by tearing at high frame rates. Turning FAST SYNC on delivers ~8ms more latency than V-SYNC OFF, while delivering entire frames without issues like tearing and jitter.
These samples were taken with a high-speed camera using Counter-Strike: Global Offensive.
NOTE Fast Sync is best tested with high FPS DX9 games.
NVIDIA Control Panel
FAST SYNC settings can be set in the NVIDIA Control Panel in the Manage 3D settings section under the Vertical sync setting.
NOTE: The default setting for Vertical Sync is to use the 3D application setting.
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