Gpu Frame Sync Technologies: G-sync Vs. Freesync, Eliminating Screen Tearing. – It started at CES, almost 12 months ago. NVIDIA announced GeForce Experience, a software solution to the problem of choosing the best graphics settings for your computer in the games you play. In console games, the developer already chooses what they feel is the right balance between visual quality and frame rate. On PC, these decisions are left to the end user. I have seen some games that try to solve the problem by limiting the number of graphic options available, but other than that, it is a problem that does not receive widespread attention. After all, PC gamers are used to fiddling with settings – it’s just an expected part of the experience. In an attempt to expand the PC gaming user base (perhaps somewhat motivated by the lack of next-gen console gains), NVIDIA came up with GeForce Experience. NVIDIA has tested a large number of games on a wide range of NVIDIA hardware, so it has a good idea of what the best settings are for each game/PC combination.

Also at CES 2013, NVIDIA announced Project Shield, which was later renamed Shield. The somewhat strange but surprisingly decent portable Android gaming system serves another function: it can be used to play PC games on the TV, streaming directly from the computer.

Gpu Frame Sync Technologies: G-sync Vs. Freesync, Eliminating Screen Tearing.

Finally, NVIDIA is quietly (and lately not so quietly) involved with Valve in the SteamOS and Steam Machine efforts (so is AMD, of course).

New Nvidia G Sync Monitors Shrink In Size To Hit Higher Frame Rates

From where I stand, it looks like NVIDIA is trying to bring aspects of console gaming to the PC. You can go a step further and say that NVIDIA seems to be very motivated to improve games in many ways than just having higher quality graphics and higher frame rates.

It all makes sense in the end. With ATI and AMD fully integrated, and Intel finally getting serious about graphics (relatively), NVIDIA will have to do more to stay relevant (and dominant) in the industry in the future. Just making good GPUs will only take the company so far.

NVIDIA’s latest effort is G-Sync, a hardware solution for displays that allows a semi-variable refresh rate determined by a supported NVIDIA graphics card. The premise is simple to understand. Displays and GPUs update content asynchronously in nature. A display panel updates itself at a fixed interval (refresh rate), usually 60 times per second (60Hz) for most panels. Game-specific displays can support a higher refresh rate of 120Hz or 144Hz. GPUs, on the other hand, render frames as quickly as possible, displaying them on the screen when they’re done.

G Sync Vs Freesync Explained

If a frame arrives in the middle of a refresh, the display ends up drawing parts of multiple frames on the screen at the same time. Drawing parts of multiple frames at the same time can result in visual artifacts or tearing, separating individual frames. You will notice tearing as horizontal lines/artifacts appear scrolling across the screen. This can be very distracting.

You can avoid tearing by keeping your GPU and display in sync. Enabling vsync does just that. The GPU will only deliver frames to the display in sync with the panel’s refresh rate. The tearing goes away, but you get a new artifact: stuttering.

Since the content of each frame in a game can vary greatly, the frame rate of the GPU can be equally variable. Once again we are in a situation where the GPU wants to render a frame out of sync with the display. With vsync enabled, the GPU will wait to deliver the frame until the next refresh period, resulting in a repeated frame in the meantime. This repeated frame shows its own stuttering. As long as you have a frame rate that doesn’t perfectly match your refresh rate, you have the potential for noticeable stuttering.

Living On The Freesync Side Of G Sync: Setup Guide, Testing & Evaluation

G-Sync aims to offer the best of both worlds. Simply put, G-Sync tries to make the display wait to refresh until the GPU is ready for a new frame. No tearing, no messing-just butter. And of course only available on NVIDIA GPUs with G-Sync display. As always, the devil is in the details.

G-Sync is a hardware solution, and in this case, the hardware is inside a G-Sync enabled display. NVIDIA swapped out the display scaler for a G-Sync board, leaving the panel and sync controller (TCON) untouched. Despite its physical location in the display chain, the current G-Sync board does not actually have a hardware scaler. For its intended purpose, the lack of any scaling hardware isn’t a big deal, since you have a more than capable GPU driving the board and handling all the scaling tasks.

G-Sync works by manipulating the display’s VBLANK (vertical blanking interval). VBLANK is the amount of time between the display rasterizing the last line of the current frame and drawing the first line of the next frame. It is called an interval because during this period of time no screen updates occur, the display remains static and shows the current frame before drawing the next one. VBLANK is a holdover from the CRT days when it was necessary to give CRTs time to start scanning over the display again. The range remains with LCD flat screens today, although not technically necessary. The G-Sync module inside the display changes VBLANK so that the display keeps the current frame until the GPU is ready to deliver a new one.

Nvidia’s G Sync: Attempting To Revolutionize Gaming Via Smoothness

With a G-Sync enabled display, when the monitor has finished drawing the current frame, it will wait until the GPU has something else ready to display before starting the next drawing process. The delay is controlled only by playing the VBLANK range.

However, there is only so much you can do to manipulate VBLANK. In current implementations, the maximum NVIDIA can capture a frame is 33.3ms (30Hz). If the next frame is not ready, the G-Sync module will tell the display to redraw the last frame. The upper limit is limited by the panel/TCON at the moment, with the only G-Sync monitor currently available reaching 6.94ms (144Hz). NVIDIA makes a point to mention that the 144Hz limit is not a G-Sync limit, but a panel limit.

The G-Sync board itself has an FPGA and 768MB of DDR3 memory. NVIDIA claims that the onboard DRAM is no bigger than what you’d normally see on a scaler inside a display. Added DRAM is a feature needed to allow for more memory bandwidth (additional physical DRAM devices). NVIDIA uses memory for many things, one of which is to store the previous frame so it can be compared to the input frame for overhead calculations.

Gt 1030

The first G-Sync module only supports DisplayPort 1.2 output, although nothing technically prevents NVIDIA from adding HDMI / DVI support in future versions. Similarly, the current G-Sync board does not support audio, but NVIDIA says that it may be added in future versions (NVIDIA’s belief here is that most gamers want something other than the built-in -in speakers on their displays). The final limitation of the first implementation of G-Sync was that it could only connect displays via LVDS. NVIDIA plans to provide V-by-One support in the next version of the G-Sync module, although there is nothing stopping it from enabling eDP support as well.

Enabling G-Sync has a small but measurable impact on frame rate performance. After the GPU renders a frame with G-Sync enabled, it starts polling the display to see if it’s in a VBLANK period or not to make sure the GPU doesn’t scan in the middle of one you scan. Polling takes about 1ms, which translates to a 3 – 5% performance impact compared to v-sync enabled. NVIDIA is working on removing all polling, but this is how it’s done for now.

NVIDIA has retrofitted the ASUS VG248QE display with a first-generation G-Sync card to demonstrate the technology. The V248QE is a 144Hz, 24″ 1080p TN display, suitable for gamers, but not the best looking display in the world. Given its current price point ($250-$280) and focus on a high refresh rate, there must be compromises (the lack of an IPS panel is the biggest here). Despite NVIDIA’s first choice of a TN display, G-Sync works well on an IPS panel, and I expect to see new G-Sync displays announced in the not-too-distant future. There’s also nothing stopping a display manufacturer from making 4K G- Sync display. DisplayPort 1.2 is fully supported, so 4K / 60Hz is the maximum you’ll see at the moment. That said, I think it’s more likely that we’ll see a 2560 x 1440 IPS display with G-Sync than one 4K models in the near term.

What Is Freesync And G Sync, And Why Should You Care?

Of course, I took the VG248QE to see the extent of the changes to use G-Sync on the display. Fortunately, disassembling the display is simple. After unscrewing the VESA mount, I had to remove the frame behind the screen. When turning on the monitor