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The AMD Big Navi / RDNA 2 architecture will power the next generation consoles and high-end graphics cards.

AMD Big Navi, Navi 2x, RDNA 2. Whatever you want to call them, AMD's next-generation GPUs are promising big performance and efficiency gains, along with feature parity with Nvidia in terms of ray tracing support. Will Team Red finally take the pole position in our GPU hierarchy and lay claim to the crown for the best graphics card, or will Nvidia's upcoming Ampere architecture spoil the party? It's too soon to say, but here's everything we know about Big Navi, including the RDNA 2 architecture, potential performance, expected release date and pricing.

We've done our best to sort fact from fiction, but even without hard numbers from AMD, we have a good idea of what to expect. The recent Xbox Series X and PlayStation 5 hardware announcements certainly add fuel to the fire, and give us realistic ideas of where Big Navi is likely to land in the PC world. Let's start at the top, with the new RDNA 2 architecture that powers Big Navi / Navi 2x. But first, here’s a brief list of what we know (or think we know) so far.

Big Navi / RDNA 2 at a Glance

Specs
Up to 80 CU / 5120 GPU cores
Performance
50% better performance per watt
Release Date
End of 2020 (if there are no delays)
Price
Unknown (but almost certainly higher than RX 5700 XT)

The RDNA 2 Architecture in Big Navi

Every generation of GPUs is built from a core architecture, and each architecture offers improvements over the previous generation. It's an iterative and additive process that never really ends. AMD's GCN architecture went from first generation for its HD 7000 cards in 2012 up through fifth gen in the Vega and Radeon VII cards in 2017-2019. The RDNA architecture that powers the RX 5000 series of AMD GPUs arrived in mid 2019, bringing major improvements to efficiency and overall performance. RDNA 2 looks to double down on those improvements in late 2020.

First, a quick recap of RDNA 1 is in order. The biggest changes with RDNA 1 over GCN involve a redistribution of resources and a change in how instructions are dispatched. In some ways, RDNA doesn't appear to be all that different from GCN. The instruction set is the same, but how those instructions are dispatched and executed has been improved. RDNA also adds working support for primitive shaders, something present in the Vega GCN architecture that never got turned on due to complications.

Perhaps the most noteworthy update is that the wavefronts — the core unit of work that gets executed — have been changed from being 64 threads wide with four SIMD16 execution units, to being 32 threads wide with a single SIMD32 execution unit. SIMD stands for Single Instruction, Multiple Data; it's a vector processing element that optimizes workloads where the same instruction needs to be run on large chunks of data, which is common in graphics workloads.

This matching of the wavefront size to the SIMD size helps improve efficiency. GCN issued one instruction per wave every four cycles; RDNA issues an instruction every cycle. GCN used a wavefront of 64 threads (work items); RDNA supports 32- and 64-thread wavefronts. GCN has a Compute Unit (CU) with 64 GPU cores, 4 TMUs (Texture Mapping Units) and memory access logic. RDNA implements a new Workgroup Processor (WGP) that consists of two CUs, with each CU still providing the same 64 GPU cores and 4 TMUs plus memory access logic.

How much do these changes matter when it comes to actual performance and efficiency? It's perhaps best illustrated by looking at the Radeon VII, AMD's last GCN GPU, and comparing it with the RX 5700 XT. Radeon VII has 60 CUs, 3840 GPU cores, 16GB of HBM2 memory with 1 TBps of bandwidth, a GPU clock speed of up to 1750 MHz, and a peak performance rating of 13.8 TFLOPS. The RX 5700 XT has 40 CUs, 2560 GPU cores, 8GB of GDDR6 memory with 448 GBps of bandwidth, and clocks at up to 1905 MHz with peak performance of 9.75 TFLOPS.

On paper, Radeon VII looks like it should come out with an easy victory. In practice, across a dozen games that we've tested, the RX 5700 XT is slightly faster at 1080p gaming and slightly slower at 1440p. Only at 4K is the Radeon VII able to manage a 7% lead, helped no doubt by its memory bandwidth. Overall, the Radeon VII only has a 1% performance advantage, but it uses 300W compared to the RX 5700 XT's 225W. In short, AMD is able to deliver roughly the same performance as the previous generation, with a third fewer cores, less than half the memory bandwidth and using 25% less power. That's a very impressive showing, and while TSMC's 7nm FinFET manufacturing process certainly warrants some of the credit (especially in regards to power), the performance uplift is mostly thanks to the RDNA architecture.

hat's a lot of RDNA discussion, but it's important because RDNA 2 appears to carry over all of that, with one major new addition: Support for ray tracing. It also supports Variable Rate Shading (VRS), which is part of the DirectX 12 Ultimate spec. There will almost certainly be other tweaks to the architecture, as AMD is making some big claims about Big Navi / RDNA 2 / Navi 2x when it comes to performance per watt. Specifically, AMD says RDNA 2 will offer 50% more performance per watt than RDNA 1, which is frankly a huge jump — the same large jump RDNA 1 saw relative to GCN. It means AMD claims RDNA 2 will deliver either the same performance while using 33% less power, or 50% higher performance with the same power, or most likely some in between solution with higher performance and lower power requirements.

The one thing we know for certain is that RDNA 2 / Big Navi / Navi 2x GPUs will all support hardware ray tracing. That will bring AMD up to feature parity with Nvidia. Note that Nvidia also has Tensor cores in its Turing architecture, which are used for deep learning and AI computations, as well as DLSS (Deep Learning Super Sampling), which has now been generalized with DLSS 2.0 to improve performance and image quality and make it easier for games to implement DLSS. So far, AMD has said nothing about RDNA 2 / Navi 2x including Tensor cores or an equivalent to DLSS, though AMD's CAS (Contrast Aware Sharpening) and RIS (Radeon Image Sharpening) do overlap with DLSS in some ways.

Regarding ray tracing, there was some question as to whether AMD would use the same BVH approach to ray tracing calculations as Nvidia, and with the PlayStation 5 and Xbox Series X announcements out of the way, the answer appears to be yes. If you're not familiar with the term BVH, it stands for Bounding Volume Hierarchy and is used to efficiently find ray and triangle intersections; you can read more about it in our discussion of Nvidia's Turing architecture and its ray tracing algorithm. While AMD didn't provide much detail on its BVH hardware, BVH as a core aspect of ray tracing was definitely mentioned, and we heard similar talk about ray tracing and BVH with the VulkanRT and DirectX 12 Ultimate announcements.

We don't know how much ray tracing hardware is present, or how fast will it be. If AMD takes the same approach as Nvidia and puts one RT core (or whatever AMD wants to call it) into each CU, the comparison between AMD and Nvidia might be easier. However, AMD could mix things up. Instead of one RT unit per CU, maybe it puts two RT cores into each WGP, or four RT cores per WGP, or some other breakdown of computing elements. The fact is, we don't know yet and won't know until AMD says more.

We also know that AMD is planning multiple Navi 2x products, and we expect to see extreme, high-end and mainstream options — though budget Navi 2x seems unlikely, given RX 5500 XT launched this year. AMD could launch multiple GPUs in a relatively short period of time, but more likely we'll see the highest performance options first, followed by high-end and eventually mid-range solutions. Some of those may not happen until 2021, however.
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