
RDNA (microarchitecture)

RDNA (Radeon DNA) is the codename for a GPU microarchitecture and accompanying instruction set architecture developed by AMD. It is the successor to their Graphics Core Next (GCN) microarchitecture/instruction set. The first product lineup featuring RDNA was the Radeon RX 5000 series of video cards, launched on July 7, 2019. The architecture is also planned to be used in mobile products. It is manufactured and fabricated with TSMC's 7 nm FinFET graphics chips used in the Navi series of AMD Radeon graphics cards.
The second iteration of RDNA was first featured in the PlayStation 5 and Xbox Series. Both consoles utilize a custom RDNA 2-based graphics solution as the basis for their GPU microarchitecture. On PC, the product line-up featuring RDNA 2 is the current Radeon RX 6000 series of video cards, which first launched in November 2020.
Architecture.
The architecture features a new processor design, although the first details released at AMD's Computex keynote hints at aspects from the previous Graphics Core Next (GCN) architecture being present for backwards compatibility purposes, which is especially important for its use (in the form of RDNA 2) in the major ninth generation game consoles (the Xbox Series X/S and PlayStation 5) to preserve native compatibility with their pre-existing eighth generation game libraries designed for GCN. It will feature multi-level cache hierarchy and an improved rendering pipeline, with support for GDDR6 memory.
Starting with the architecture itself, one of the biggest changes for RDNA is the width of a wavefront, the fundamental group of work. GCN in all of its iterations was 64 threads wide, meaning 64 threads were bundled together into a single wavefront for execution. RDNA drops this to a native 32 threads wide. At the same time, AMD has expanded the width of their SIMDs from 16 slots to 32 (aka SIMD32), meaning the size of a wavefront now matches the SIMD size.
RDNA also introduces working primitive shaders. While the feature was present in the hardware of the Vega architecture, it was difficult to get a real-world performance boost from and thus AMD never enabled it. Primitive shaders in RDNA are compiler-controlled.
The display controller in RDNA has been updated to support Display Stream Compression 1.2a, allowing output in 4k@240 Hz, HDR 4K@120 Hz, and HDR 8K@60 Hz.
Instruction set.
AMD's GPUOpen website hosts a PDF document aiming to describe the environment, the organization and the program state of AMD “RDNA” Generation devices. It details the instruction set and the microcode formats native to this family of processors that are accessible to programmers and compilers.
Differences between GCN and RDNA.
There are architectural changes which affect how code is scheduled:
RDNA 2.
RDNA 2 (also "RDNA2") is the successor to the RDNA microarchitecture, which was publicly announced for release in Q4 2020. According to statements from AMD, RDNA 2 would be a "refresh" of the RDNA architecture.
More information about RDNA 2 was made public on AMD's Financial Analyst Day on March 5, 2020. AMD claimed that it would provide a 50% performance-per-watt improvement over RDNA, with increases in clock speed and instructions-per-clock. Additional features confirmed by AMD include real-time, hardware accelerated ray tracing, Infinity Cache™, mesh shaders, sampler feedback and variable rate shading. The company announced that RDNA 2 would be used in next-generation gaming consoles and PC graphics cards code-named "Navi 2X" and also nicknamed as "Big Navi".
AMD unveiled the Radeon RX 6000 series, its next-gen RDNA 2 graphics cards at an online event on October 28, 2020. The lineup initially consists of the RX 6800, RX 6800 XT and RX 6900 XT. The RX 6800 and 6800 XT launched on November 18, 2020, with the RX 6900 XT being released on December 8, 2020. Further variants including a Radeon RX 6700 (XT) series based on Navi 22, later launched on March 18, 2021.
Usage in next-generation video game consoles.
The RDNA 2 graphics microarchitecture is used in the PlayStation 5 from Sony, Xbox Series X and Series S consoles from Microsoft, with proprietary tweaks and different GPU configurations in each system's implementation.
RDNA 3.
RDNA 3 is the successor to the RDNA 2 microarchitecture and is scheduled for late 2021 as per AMD's gaming GPU roadmap. It was reported that the RDNA 3 GPUs will utilize the multi-chip module for its design, allowing for considerable performance gains over the previous generation.