A grab bag of other improvements and changes
The GTX 1080 and the Pascal architecture introduce a number of smaller improvements and changes, as well. We won't be covering these in depth today, but some of them are worth taking a brief look at. For more information, we'd recommend checking out Nvidia's excellent GeForce GTX 1080 whitepaper.
Nvidia notes that competitive gamers who run titles like Counter-Strike: Global Offensive at high frame rates often leave v-sync off to let the graphics card run as fast as possible and to minimize input latency, at the expense of introducing tearing. When you're rendering frames at multiple hundreds of FPS, it makes sense that tearing would be rampant. Fast Sync is a new frame output method that's meant to eliminate tearing while maintaining most of the competitive benefits that running with vsync off entails. To accomplish that ideal, Nvidia says it decoupled the rendering and display stages of the graphics pipeline. With Fast Sync on, the card can still render frames as fast as possible, but it'll only send completed frames to the display, avoiding tearing.
To make that principle work, the Fast Sync logic adds a third buffer—the "last rendered buffer"—to the traditional front- and back-buffers of a graphics pipeline with vsync on. This new buffer contains the last complete frame written to the back buffer. It holds this frame until the front buffer finishes sending a frame to the display, at which point it's renamed to the front buffer and the display begins writing out the completed frame held within.
Nvidia emphasizes that no copying between buffers occurs in this process. Rather, the company notes that it's much more efficient to simply rename buffers on the fly. Once the last rendered buffer becomes the front buffer and scanout begins, a bunch of buffer-naming musical chairs occurs in the background while the display is scanning out so that rendered frames have places to go in the meantime. When the display scanout completes and the music stops, whichever buffer had assumed the role of the "last rendered buffer" prior to that point becomes the front buffer, and the cycle repeats. Nvidia says new flip logic in Pascal is responsible for managing this process.
Fast Sync adds a bit of latency to the gameplay experience, as the annoyingly vague chart above purports to show. Still, as someone who's exceptionally sensitive to tearing, I'd welcome slightly more input latency in trade for banishing that ugly visual artifact from my life.
To be clear, Fast Sync is not a replacement for G-Sync or FreeSync variable-refresh-rate monitors—it's an interesting but separate complement to those technologies. We'll need to play with this tech and see how it works in practice.
SLI and Pascal
We've already covered the changes to SLI that Nvidia is making with its Pascal cards. To recap, the company is discontinuing internal development of SLI profiles for three- and four-way SLI setups. It's instead putting its weight entirely behind two-way SLI setups, instead. Extreme benchmarkers will still be able to get three- and four-way SLI profiles for use with apps like 3DMark, but for all intents and purposes, two-way SLI is the way of the future.
Running two-way SLI at its maximum potential with the GTX 1080 requires a new "high-bandwidth" SLI bridge that links both sets of SLI "fingers" present on GTX 1080s. With the proper bridge, the GTX 1080's SLI link runs at 650MHz. Older "LED SLI bridges" will also run at this speed, but the ribbon-cable bridge included with many motherboards will only run at 400MHz with Pascal cards. Nvidia says the net result of this change is a doubling in SLI bandwidth compared to past implementations of the technology.
If Nvidia's internal numbers are to be believed, HB SLI has tangible benefits on in-game smoothness. The company ran Shadows of Mordor on an 11520x2160 display array to show off the feature, and the frame time plot of that benchmark suggests that the added bandwidth helps reduce worst-case latency spikes.
HDR content and higher-res display support
One of the major updates that AMD has been touting for its next-gen Radeons has been a bevy of features related to high-dynamic-range gaming and video playback, and Pascal appears just as ready for that next-generation content.
Nvidia's Maxwell cards already came with support for 12-bit color, the BT.2020 wide color gamut, and the SMPTE 2084 electro-optical transfer function (EOTF). Pascal adds support for 60Hz 4K HEVC video decoding with 10- or 12-bit color, 60Hz 4K HEVC encoding with 10-bit color for recording or streaming HDR content, and DisplayPort 1.4's metadata transport spec for HDR over that connection. Pascal cards will also be able to perform game-streaming in VR with a compatible device, like Nvidia's Shield Android TV.
Nvidia is also beefing up high-res display support with Pascal and the GTX 1080. While the new card can still run only four active displays, it can now run monitors that max out at 8K (7680x4320) using two DisplayPort 1.3 cables. The GTX 1080 supports HDMI 2.0b with HDCP 2.2, and though it's just DisplayPort 1.2-certified right now, it's ready for the upcoming, higher-bandwidth DisplayPort 1.3 and DisplayPort 1.4 standards.
Now that we've covered some of the biggest changes in Pascal for consumers, let's talk about the GTX 1080 Founders Edition card itself.