Unreal Engine – AMD Radeon RX 6900 XT Performance

Introduction

Both NVIDIA and AMD have released several new GPUs in the final months of 2020, with one of the more recent being the AMD Radeon RX 6900 XT 16GB. This officially launched on December 8th, but due to extremely tight supply, we have not been able to get our hands on one to test until just recently. In fact, we still have not been able to purchase a card ourselves, but our friends at Linus Media Group were able to loan us a card so we could perform our testing.

While gaming is almost always a major focus during these GPU launches, professional applications have been leveraging the power available in these cards to greatly increase performance. Unreal Engine straddles the line between these two use cases, being used for game development to film and visual effects. Unlike some rendering engines that require CUDA, Unreal is more agnostic and even uses Microsoft’s DXR API for its ray tracing, letting us see what AMD’s new ray-tracing capabilities are.

If you want to see the full specs for the latest GPUs from NVIDIA and AMD, we recommend checking out the NVIDIA GeForce RTX 30 Series and AMD Radeon RX Graphics Cards product pages. But at a glance, here are what we consider to be the most important specs:

While specs rarely line up with real-world performance, the biggest thing to note is that the AMD Radeon 6900 XT 16GB is at the top of the product stack from AMD and has an MSRP that is $300 higher than the NVIDIA GeForce RTX 3080 10GB, or $500 lower than the GeForce RTX 3090 24GB. Based on price alone, this means that we (hopefully) will see better performance from the 6900 XT than the RTX 3080.

However, something else important to notice is that VRAM’s usefulness in Unreal greatly depends on your particular workflow. Typically things that impact how much VRAM are ray tracing effects, number of textures and their sizes, number of models and their poly counts, particle systems, and the render resolution.

Note that the current supply is so poor that you will be lucky to find many of these cards for anywhere near the MSRP. However, we typically use the MSRP as a baseline for price in order to rule out fluctuations due to different brands, sales, and scarcity. The actual cost you will likely need to pay for either an AMD or NVIDIA card is likely to be quite a bit different, so keep that in mind as you read this article.

Test Setup

Listed below is the specifications of the system we will be using for our testing:

*All the latest drivers, OS updates, BIOS, and firmware applied as of December 1st, 2020

To test each GPU, we will be using the AMD Threadripper 3970X. Due to its speed at compiling shaders, building lighting, etc, Threadripper has become the go-to for Unreal development.

For the testing itself, we will be using four sample scenes from the marketplace with some modifications to make testing easier. These sample scenes are a much better representation of what someone in Virtual Production or Architecture may work with than a video game. Eventually, we would like to have custom maps for these tests, however, due to time constraints for this launch, these will work just fine. Here are some relevant stats for each scene.

Also of note, none of these tests use Nvidia’s DLSS. We are comparing the raw power of each card.

Raw Benchmark Results

While we are going to go through our analysis of the testing in the next section, we are providing the raw results for those that want to dig into the details. If there is a specific sort of project you work with, you can compare it to the scene that most closely matches your work.

GPU Performance Analysis

What we see across all of our test scenes and settings is fairly consistent. There are clearly two different answers to how well the AMD Radeon RX 6900XT performs. In Rasterized workloads, AMD is neck and neck with the more expensive NVIDIA RTX 3090. This is a major step forward for AMD. It has been a long time since they have been this competitive with NVIDIA's top end.

On the other hand, when we look at ray-traced workloads, the 6900XT struggles to keep up. On average it is close to the last generation’s 2080 Ti, however that places it between the RTX 3060 Ti and RTX 3070. Both of which cost significantly less than the Radeon. This is AMD’s first try at ray-traced hardware, so it’s respectable. Hopefully, the next generation will bridge the gap.

This is unfortunate as the Radeon’s 16GB VRAM makes it very appealing to higher-end workloads. In our tests, enabling ray tracing can as much as double the amount of VRAM being used in a scene. We can see this in the ArchViz 4K scene where the Radeon was one of the few that didn’t crash because of running out of memory. However, in every other scene where VRAM isn’t an issue, NVIDIA performed better.

How well does the AMD Radeon RX 6900 XT perform in Unreal Engine 4.26?

The AMD Radeon RX 6900 XT performed admirably in traditional rasterized workloads. It consistently matched the more expensive NVIDIA RTX 3090. The generous 16GB of VRAM will prove useful to many users that need the extra data.

However, when ray tracing is enabled, the RTX 6900 XT performed poorly. Usually beaten by the NVIDIA RTX 3070, which costs half as much. Professional users that working with ray tracing, even if it is only occasionally, would be better served by the offerings from NVIDIA.

NVIDIA's RTX 3090 is still the top all-around choice for Unreal Engine. If you don’t need the extra VRAM, NVIDIA's 3080 is a strong contender at a very reasonable price point.