Earlier this week, news surfaced of a leaked Nvidia driver that could supposedly enable G-Sync on any mobile or desktop display. The author used this driver to argue that Nvidia’s GeForce was nothing but a DRM scam, and that the Altera Arria V FPGA inside the G-Sync module was nothing but a DRM mechanism designed to ensure that G-Sync was limited to Nvidia-approved monitors and video cards.
Gamenab’s various claims run the gamut from flatly incorrect to highly dubious, but there is a kernel of accuracy to them — specifically, the driver the website leaked does enable an early version of G-Sync support on at least one laptop.
Setting the record straight on G-Sync support
Gamenab makes a number of inflammatory accusations concerning G-Sync support. According to the site, G-Sync is “a kind of DRM component protection,” CUDA “was made to force the developers to work on an Nvidia GPU,” and the Altera FPGA inside the G-Sync module “does nothing else than confirm that the module is right here.”
Two of these claims are factually untrue. While it’s true that CUDA is Nvidia’s own proprietary language, it debuted in 2007 — two years before OpenCL 1.0 or DirectCompute were released. Nvidia wrote their own proprietary language for GPGPU applications because, at the time, there was nothing else like it on the market. Gamenab also claims that G-Sync uses an Altera FPGA solely as a DRM solution. In addition to linking to the wrong literature on the topic (Gamenab claims the chip is a Stratix when it’s actually an Altera Arria V GX), Nvidia absolutely denies that the purpose of the chip is as a DRM conduit. The reason Nvidia had to build its own ASIC in the first place is because existing desktop monitors didn’t support the hardware features G-Sync requires.
Nvidia G-Sync
Never let facts get in the way of a good story. Image by Anandtech
Gamenab also claims that this driver enables G-Sync support on any desktop monitor that supports DisplayPort 1.2. We tested both the Dell UP2414Q and an Asus PQ321Q display. Neither showed any sign of G-Sync compatibility. The entire reason that Nvidia built G-Sync as a specialized solution is because there were no ASICs available on the desktop market that would allow it to synchronize frame display between the GPU and the monitor. Even the FreeSync / Adaptive-Sync standard backed by AMD required modifications to the DisplayPort standard and a new set of supporting monitors. In short, there’s no reason to expect this driver to magically enable G-Sync on any standard desktop display.
Finally, despite Gamenab’s claims to the contrary, this is not a “hacked” driver. It’s a leaked driver from one of Nvidia’s OEM partners that was designed to enable an early form of mobile G-Sync support.
Whew. Alright, now that we’ve covered all the dross, let’s talk about the good stuff. Mobile G-Sync? It’s definitely happening.
Previewing mobile G-Sync
While this driver is worthless for enabling desktop G-Sync, it installed perfectly on an Asus G751J laptop. For those of you who don’t recall, the basic idea of G-Sync is that game output can be greatly smoothed by synchronizing the GPU frame buffer with the LCD’s output.
The traditional method of preventing screen tearing in a game is to use Vertical Sync, or V-Sync, but while V-Sync’s locked framerate prevents half-displayed updates that result in a fractured image, the frame rate drops precipitously if the GPU can’t lock its frame output to the refresh rate. The graph below shows an example of V-Sync frame rates spiking and dropping between 30 and 60 fps depending on how long it takes the GPU to finish a frame (the green line is the GPU’s output, the red line is the actual displayed frame rate).
V-Sync frametime
V-Sync pulls the frame rate down if it can’t maintain 60 FPS. Image courtesy of Tech Report
The difference between G-Sync and V-Sync is captured in the video below, albeit imperfectly — without a high speed camera it’s difficult to perfectly differentiate the two. Nonetheless, the V-Sync video on the left has a subtle jerkiness to it that the G-Sync camera on the right lacks.
We confirmed that the pendulum demo ran perfectly on our Asus notebook, then fired up Skyrim to check a shipping title. Here’s what the frame times look like for Skyrim when G-Sync vs. V-Sync is used — bearing in mind, obviously, that this driver is still in alpha.
Elder Scrolls Skyrim
Elder Scrolls Skyrim — V-Sync enabled only
Elder Scrolls Skyrim -- G-Sync Enabled
Elder Scrolls Skyrim — G-Sync enabled
The frame rate still jumps in a handful of places, but delivery and timing are much tighter with the G-Sync solution. That’s the advantage of the technology, and the idea of seeing it in enthusiast hardware is downright exciting. G-Sync just feels better in the majority of cases, especially if you only have a 60 Hz refresh rate on your LCD.
The mobile support question
Back when Nvidia announced G-Sync, the company said it was exploring mobile options as well. This leaked alpha driver is proof that the company is still working to build that support into shipping hardware, but it’s not clear when we’ll see shipping solutions. The fact that G-sync worked on a single Asus laptop and with one particular title doesn’t mean that the support is finalized or working across all games / laptops.
Unlike desktop monitors, which have independent chips for controlling their own timing and other characteristics, mobile displays tend to take their settings directly from the GPU itself. That’s how AMD was able to demo its first iteration of FreeSync on a mobile display more than a year ago — the embedded DisplayPort (eDP) standard contains certain features that conventional DisplayPort 1.2 lacked.
Nvidia has declined to say exactly how they enable G-Sync on desktop hardware or precisely what the mobile solution looks like, which has fueled speculation that their solution is substantially identical to the Adaptive-Sync standard now baked into DisplayPort 1.2a. Similarly, it’s not clear which laptops, if any, might receive a retroactive update to enable G-Sync support — while customers would obviously appreciate the option, companies like Asus have financial incentive to restrict their validation process to new systems.
Enabling G-Sync
Laptop users who want to experiment with the driver can find it here, though we advise being careful to back up important data. If the driver works, the option to enable G-Sync will appear in the Nvidia Control Panel as shown above.
