In this article, we’ll take a look at some of the exclusive technologies that Nvidia GeForce RTX 4000 generation graphics cards can provide. We are going to explain the most significant new features currently supported by the GeForce graphics card ecosystem and perform tests showing how they affect performance in Cyberpunk 2077 with the new Phantom Liberty expansion. And we’ll also take a look at what they’re doing to image quality.
Reflex: How to have the fastest reactions
Now is a good time to mention the Nvidia Reflex technology, exclusive to Nvidia GeForce graphics cards, which is important for competitive gaming. Reflex aims at helping with precisely the problem that, for competitive gamers, is the latency between the input and the display, or you can also say between the action in the game (including the actions of the opponents) and their display on the monitor. This latency represents the time that elapses before an event in the game – such as an enemy emerging from behind a wall – is actually reflected on the monitor. Thus, it is the time that is added as a negative disadvantage to the player’s actual reaction time. The lower this latency, the more advantage the player has, because they can start reacting before the opponent. In competitive multiplayer gaming, the lowest possible latency should directly improve a competitor’s potential.
Previous solutions aimed at reducing latency (such as Low Latency Mode) work by eliminating the frame queue in the driver, but Reflex goes beyond the capabilities of these technologies. Reflex is based on a component (Reflex SDK) that developers integrate directly into the game, opening up deeper possibilities for reducing the various responses and delays that occur between input and output.
In addition to the Reflex SDK and its integration into games, Reflex also offers input latency measurement for peripherals such as mice, keyboards, and even monitor latency. This Reflex Latency Analyzer feature works with supported hardware and monitors with G-Sync. For most gamers, the main thing that will probably be relevant is the Reflex SDK and its integration in games, which is not tied to owning specific mice or monitors.
You always have some latency when you are gaming, and many things are the source of that latency at the same time. There’s not much you can do about network connection latency (if you already have the best connection possible or affordable to you), which is the lag or “ping” of packets between you and the game server. Nvidia Reflex tries to mitigate another latency that occurs at your computer, which it calls “System Latency”. This is “contributed” to by the input lag of your mouse, keyboard, and their signals being processed by the operating system at the beginning and then by the delay between when the finished frame from the graphics card is sent to the monitor and when it is actually displayed at the end (the monitor has a certain panel response as well as the input lag of the electronics).
Between these peripheral and monitor latencies then lies an amount of latency that is determined by the game itself and its code, which has to process the input of the player(s), calculate what they will do to the game scene, how all the objects in it will behave. This part takes place mainly on the gaming computer’s processor, and Nvidia calls it “Game Latency”. The game then tells the graphics driver to render a frame of the game that shows the result of this. The time taken by production of this frame on the GPU is then the rendering latency (“Render Latency”).
When your game is running at a high frame rate due to sufficient GPU performance, the duration of frames and the time it takes to process them is shortened by inverse proportionality, so high performance itself reduces game latency and rendering latency. But high FPS alone isn’t all you need, because how the game works can artificially increase latency. Adding Reflex to games in conjunction with GeForce graphics drivers tries to eliminate this as much as possible. The main way is by reducing the various downtimes that can build up in a game with better low-latency synchronization to ensure that frames go to the monitor for rendering as soon as possible.
The first step is to limit the part of the game running on the CPU from generating excess frames for further steps of the rendering running on the GPU (which is called CPU Back Pressure). When this happens, a queue of pending frames is created, but each such worsens latency. Another such queue can then also be created in the part running on the GPU in the so-called “Render Queue”. Reflex aims to make the entire game complex running on the CPU and GPU work in a “just in time” style, i.e., the finished frame submissions from CPU processing arrive at the GPU at about the time the GPU can start working on them (without delay), and then they can again be sent straight to the monitor as quickly as possible.
Low Latency Boost for GPUs
A game with Reflex integrated should therefore regulate the pace at which the CPU part produces new frames if the GPU can’t process them as quickly. This would create the described negative CPU Back Pressure phenomenon and increase the latency of the game. Reflex therefore dynamically controls when frame submissions are fed to the GPU.
At the same time, GPU drivers can increase the GPU clock speed to render images faster, so Reflex also communicates with the GPU clock speed control. This feature is called Low Latency Boost and has the ability to override the normal power management of the GPU, which tries to optimize its clock speed for higher overall power efficiency. Low Latency Boost should be able to dial the clock speeds up temporarily even at the cost of efficiency loss in situations where rendering delays are imminent.
Ironically, this Low Latency Boost can help with games where the GPU load is relatively low, because they are not demanding and are mainly limited by the CPU. In such situations, graphics cards tend to run in power saving modes and at lower clock speeds. But these can lead to higher rendering latencies in competitive games. Low Latency Boost therefore force-activates the highest-performance mode even in such a situation, where the GPU is underutilized, in order to reduce rendering latencies as much as possible. However, this leads to an increase in GPU power draw, where an undemanding game where you expect low power draw instead consumes significant watts (and generates higher GPU temperatures). For example, for laptop gaming, Nvidia therefore makes it possible to turn Low Latency Boost off and still leave Reflex on without it.
In short, according to Nvidia, Reflex tries to prevent the CPU from running ahead and accumulating a queue of multiple pending frames (worsening rendering latency) in situations where the game is limited by GPU performance (i.e. in a challenging scene where FPS drops). Conversely, in situations where the limit is on the CPU side, Reflex tries to minimize the time it takes for frames to be rendered by the GPU (rendering latency) and send them to display as fast as possible by keeping the GPU clock speeds high.
Available with GeForce GTX 900 and newer
The Reflex feature only works on Nvidia GeForce graphics cards, but also supports older generations (back to GeForce GTX 900). Low Latency Boost should work best on GeForce RTX 3000 and newer graphics cards that have better ability to increase clock speeds when it is activated.
Improving responsiveness with Reflex should obviously be most important for games with PvP multiplayer and competitive multiplayer in general, and eSports games – including popular titles like Fortnite, Valorant, Apex Legends, Call of Duty.
Reflex and Frame Generation
While at its core, Reflex is most interesting for such competitive players, the technology became important in games where latency would otherwise not be much of a consideration with the advent of DLSS 3 (and later DLSS 3.5), which introduced frame generation.
As stated before, you always have some latency when gaming, it’s created by the input device and the processing of those inputs in the game, the physical calculations and rendering, the input lag of the monitor electronics, and even the pixel response of the panel. All of this adds up to a rather large sum of milliseconds. Frame Generation, as mentioned, has to delay displaying of the last rendered frame (since it will only follow after the artificially generated one is displayed) and thus adds some extra latency itself. It doesn’t have to be that many milliseconds versus all the other factors combined, so it may not always matter significantly, but some deterioration is always occurring there by definition. There has been a recent push to shorten and eliminate these latencies, at least for fast competitive games, while frame generation is going in the opposite direction.
Therefore, DLSS 3/3.5 has integrated Reflex technology when using frame generation, which in turn aims to reduce latency. Reflex cannot remove the inherent latency increase created by frame generation, i.e. the negative effect of having to buffer at least one future frame to interpolate the previous one. What Reflex does do, however, is suppress the other sources of latency (namely, game latency and rendering latency before it is the turn of frame generation).
Reflex’s help is therefore about compensating frame generation’s negative impact. In case you start with a game already optimized for low latency by turning on Reflex, and then you activate the frame generation feature on top of that, your latency will of course go up, because Reflex has already used the sources of latency reduction and can’t do anything more.
