Enabling Nvidia Reflex in iRacing

Last week iRacing included in the simulator the possibility to activate this new feature of Nvidia drivers called Reflex. Supposedly it improves the latency in compatible cards and devices, although it is not necessary to expect miracles, but less is nothing and it is appreciated that this kind of technologies are included in the simulator.

At the moment, the following devices are supported:

The latest drivers available today are as follows:

• Nvidia Drivers 511.23 (14/01/22)

Here is the clarification from the notes on how it works:

When enabled in the graphics options (top right), and when the Simulator is GPU-bound, this option reduces the Simulator’s latency when rendering by enabling low latency mode in the device driver. When enabled with “boost mode”, it also keeps the GPU clock speed higher when the Simulator is CPU-bound, which can also help a bit. Enabling NVIDIA Reflex in the graphics options can help reduce this latency, mainly when the Simulator is GPU-bound. When the Simulator is CPU bound, there is not much Reflex can do.

The pre-rendered max frame widgets are hidden when Reflex is enabled, as it takes over and keeps it close to zero.

And here’s the staff explanation:

Reflex focuses on the virtual pipeline between the CPU, GPU and monitor.

Under normal circumstances, the CPU works as fast as it can to render the frames and then passes them to the GPU. The GPU works as fast as it can to process those frames and passes them to your monitor.

What we mean when we say “CPU limited” is that the CPU takes longer on a frame than the GPU, so the GPU finishes a frame and sits idle until the CPU sends the next frame. In this case Reflex does nothing.

When GPU limited, the opposite happens, the CPU is producing frames faster than the GPU can consume them. This means that the GPU has to manage a backlog of frames every time it is going to grab one, and this leads to a number of strange problems.

In this case of GPU limitation, Reflex will act as a messenger from the GPU to the CPU, telling it when the GPU is ready for a new frame. This means that the CPU does less work to produce frames that will never be used, and the GPU has to sort out fewer stale frames that are actually a few ticks old. Reducing the number of frames left in the queue is the goal of Reflex. As this whole loop is how you receive information about your own inputs (such as direction), it means you can see the effects of your inputs a little faster.

In short, it doesn’t seem to have any side effects, so it’s worth turning it on at least to 1.

See you on the track!