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 N7 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 X and Series S consoles. Both consoles utilize a custom RDNA 2-based graphics solution as the basis for their GPU microarchitecture. On PC, RDNA 2 is featured in the 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:

Single cycle instruction issue:
GCN issued one instruction per wave once every 4 cycles.
RDNA issues instructions every cycle.
Wave32:
GCN used a wavefront size of 64 threads (work items).
RDNA supports both wavefront sizes of 32 and 64 threads.
Workgroup Processors:
GCN grouped the shader hardware into "compute units" (CUs) which contained scalar ALUs and vector ALUs, LDS and memory access. One CU contains 4 SIMD16s which share one path to memory.
RDNA introduced the "workgroup processor" ("WGP"). The WGP replaces the compute unit as the basic unit of shader computation hardware/computing. One WGP encompasses 2 CUs. This allows significantly more compute power and memory bandwidth to be directed at a single workgroup. In RDNA, 1 CU is one half of a WGP.

RDNA 2 

RDNA 2 (also RDNA2) is the successor to the RDNA microarchitecture. It was first publicly announced in early 2020 with a projected 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.

On May 31, 2021, AMD launched the RX 6000M series of GPUs designed for laptops. These include the RX 6600M, RX 6700M, and RX 6800M. These were made available beginning on June 1, 2021.

It will be used as a graphic architecture for Samsung Electronics' mobile AP to be released in 2022.

Usage in video game consoles 
Custom configurations of 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 modifications in each system's implementation.

On June 1, 2021 AMD's CEO Dr. Lisa Su and Tesla, Inc.'s CEO Elon Musk confirmed that the entertainment systems of Tesla's new Model S and Model X are powered by RDNA 2.

Valve announced on July 15, 2021 that their new Steam Deck is set to be released in December 2021 and will feature the RDNA 2 architecture.

RDNA 3 

RDNA 3 is the upcoming successor to the RDNA 2 microarchitecture and is scheduled for a 2022 release as per AMD's gaming GPU roadmap.

See also 
 List of AMD graphics processing units
 AMD Radeon Software
 GPUOpen
 ROCm

References

External links 
 RDNA's official page on AMD.com
 RDNA 2's official page on AMD.com
 AMD RDNA 1.0 Instruction Set Architecture – Reference Guide - developer.amd.com
 AMD RDNA 2 Instruction Set Architecture – Reference Guide - developer.amd.com

Advanced Micro Devices microarchitectures
Computer-related introductions in 2019
Graphics microarchitectures