RDNA (microarchitecture)

RDNA (Radeon DNA[2][3]) 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.[1][4] The architecture is also planned to be used in mobile products.[5] It is manufactured and fabricated with TSMC's 7 nm FinFET graphics chips used in the Navi series of AMD Radeon graphics cards.[6]

AMD RDNA
Release dateJuly 7, 2019 (July 7, 2019)[1]
Fabrication processTSMC 7 nm
History
PredecessorGraphics Core Next 5
SuccessorRDNA 2
A generic block diagram of a GPU.

The second iteration of RDNA was first featured in the PlayStation 5[7] and Xbox Series.[8] Both consoles utilize the RDNA 2-based graphics 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.[9]

Architecture
Die shot of the RX 5500 X's RDNA GPU

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.[10]

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.[10]

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.[10][11]

Instruction set
Main article: Graphics Core Next: 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.[12]

The RDNA instruction set is owned by AMD (that also owns the X86-64 instruction set).

Differences between GCN and RDNA

There are architectural changes which affect how code is scheduled:

  1. Single cycle instruction issue:
    • GCN issued one instruction per wave once every 4 cycles.
    • RDNA issues instructions every cycle.
  2. Wave32:
    • GCN used a wavefront size of 64 threads (work items).
    • RDNA supports both wavefront sizes of 32 and 64 threads.
  3. 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
AMD RDNA 2
Release dateNovember 18, 2020 (November 18, 2020)
CodenameNavi 2X
Fabrication processTSMC "Enhanced" 7nm
History
PredecessorRDNA
SuccessorRDNA 3

RDNA 2[13] (also RDNA2)[14] is the successor to the RDNA microarchitecture, which was publicly announced for release in Q4 2020.[14][15] According to statements from AMD, RDNA 2 would be a "refresh" of the RDNA architecture.[16]

More information about RDNA 2 was made public on AMD's Financial Analyst Day on March 5, 2020.[17][15][18] AMD claimed that it would provide a 50% performance-per-watt improvement over RDNA, with increases in clock speed and instructions-per-clock.[19] Additional features confirmed by AMD include real-time, hardware accelerated ray tracing, Infinity Cache™, mesh shaders, sampler feedback and variable rate shading.[19][9] The company announced that RDNA 2 would be used in next-generation gaming consoles and PC graphics cards[19] code-named "Navi 2X" and also nicknamed as "Big Navi".[20]

AMD unveiled the Radeon RX 6000 series, its next-gen RDNA 2 graphics cards at an online event on October 28, 2020.[21][22] The lineup initially consists of the RX 6800, RX 6800 XT and RX 6900 XT.[23][24] The RX 6800 and 6800 XT launched on November 18, 2020, with the RX 6900 XT being released on December 8, 2020.[9] The RX 6700 and RX 6700 XT variants, which is based on Navi 22 is expected to launch in the first half of 2021.[25][26][27]

Usage in next-generation video game consoles

The RDNA 2 graphics microarchitecture is used in the PlayStation 5[7][28] from Sony, Xbox Series X and Series S consoles[8] from Microsoft, with proprietary tweaks and different GPU configurations in each system's implementation.

RDNA 3
AMD RDNA 3
Fabrication processTSMC
History
PredecessorRDNA 2

RDNA 3 is the successor to the RDNA 2 microarchitecture and is planned to be released in 2022.[29] 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.[30]

See also

References
  1. AMD press release: "AMD Announces Next-Generation Leadership Products at Computex 2019 Keynote". AMD.com. Retrieved October 5th, 2019
  2. Smith, Ryan (26 May 2019). "Home> GPUs AMD Teases First Navi GPU Products: RX 5700 Series Launches in July, 25% Improved Perf-Per-Clock". AnandTech. Retrieved 21 June 2019.
  3. "AMD RDNA Architecture".
  4. AMD launches RX 5700 XT and RX 5700 GPUs with RDNA architecture
  5. Smith, Ryan (10 June 2019). "GPUs AMD Announces Radeon RX 5700 XT & RX 5700: The Next Gen of AMD Video Cards Starts on July 7th At $449/$379". AnandTech. p. 1. Retrieved 21 June 2019.
  6. "AMD Radeon RX 5700 XT release date, price, specs, and performance". PCGamesN. Retrieved 28 June 2019.
  7. Funk, Ben (December 12, 2020). "Sony PS5 Gets A Full Teardown Detailing Its RDNA 2 Guts And Glory". Hot Hardware. Retrieved January 3, 2021.
  8. Smith, Ryan. "Microsoft Drops More Xbox Series X Tech Specs: Zen 2 + RDNA 2, 12 TFLOPs GPU, HDMI 2.1, & a Custom SSD". www.anandtech.com. Retrieved 2020-03-19.
  9. Judd, Will (October 28, 2020). "AMD unveils three Radeon 6000 graphics cards with ray tracing and RTX-beating performance". Eurogamer. Retrieved October 28, 2020.
  10. Smith, Ryan (10 June 2019). "GPUs AMD Announces Radeon RX 5700 XT & RX 5700: The Next Gen of AMD Video Cards Starts on July 7th At $449/$379". AnandTech. p. 2. Retrieved 21 June 2019.
  11. Stobing, Chris (10 June 2019). "AMD Details Radeon RX 5700 'Navi' GPUs: Here's What You Need to Know". PC Magazine. Ziff Davis, LLC. Retrieved 21 June 2019.
  12. "AMD RDNA 1.0 Instruction Set Architecture". GPUOpen.
  13. "AMD Investor Relations presention (PDF)". AMD.com. Advanced Micro Devices. 2019. Retrieved 2020-02-08.
  14. "Navi Refresh and RDNA2 Both In 2020, According to AMD". anandtech.com. AnandTech. 2020-01-28. Retrieved 2020-02-08.
  15. "AMD 'Big Navi' GPU might be right around the corner – but don't hold your breath". techradar.com. TechRadar. 2020-02-03. Retrieved 2020-02-08.
  16. "AMD to Introduce New Next-Gen RDNA GPUs in 2020, Not a Typical 'Refresh' of Navi". tomshardware.com. Tom's Hardware. 2020-01-29. Retrieved 2020-02-08.
  17. "AMD will unveil RDNA 2 graphics cards on March 5". pcgamesn.com. PCGamesN. 2020-01-29. Retrieved 2020-02-08.
  18. March 2020, Paul Alcorn 05. "AMD Financial Analyst Day 2020: CPU and GPU Roadmaps, X3D Die Stacking Revealed". Tom's Hardware. Retrieved 2020-03-07.
  19. Smith, Ryan. "AMD's RDNA 2 Gets A Codename: "Navi 2X" Comes This Year With 50% Improved Perf-Per-Watt". www.anandtech.com. Retrieved 2020-03-07.
  20. Smith, Ryan. "AMD's RDNA 2 Gets A Codename: "Navi 2X" Comes This Year With 50% Improved Perf-Per-Watt". www.anandtech.com. Retrieved 2020-03-16.
  21. Garreffa, Anthony (September 9, 2020). "AMD to reveal next-gen Big Navi RDNA 2 graphics cards on October 28". TweakTown. Retrieved September 9, 2020.
  22. Lyles, Taylor (September 9, 2020). "AMD's next-generation Zen 3 CPUs and Radeon RX 6000 'Big Navi' GPU will be revealed next month". The Verge. Retrieved September 10, 2020.
  23. "AMD Teases Radeon RX 6000 Card Performance Numbers: Aiming For 3080?". anandtech.com. AnandTech. 2020-10-08. Retrieved 2020-10-25.
  24. "AMD Announces Ryzen "Zen 3" and Radeon "RDNA2" Presentations for October: A New Journey Begins". anandtech.com. AnandTech. 2020-09-09. Retrieved 2020-10-25.
  25. Mujtaba, Hassan (2020-11-30). "AMD Radeon RX 6700 XT 'Navi 22 GPU' Custom Models Reportedly Boost Up To 2.95 GHz". Wccftech. Retrieved 2020-12-03.
  26. Tyson, Mark (December 3, 2020). "AMD CEO keynote scheduled for CES 2020 on 12th January". HEXUS. Retrieved 2020-12-03.
  27. Cutress, Ian (January 12, 2021). "AMD to Launch Mid-Range RDNA 2 Desktop Graphics in First Half 2021". AnandTech. Retrieved January 4, 2021.
  28. Gartenberg, Chaim (March 18, 2020). "Sony reveals full PS5 hardware specifications". The Verge. Retrieved January 3, 2021.
  29. Soutter, Neil (January 25, 2021). "AMD RX 7000 series could be a performance monster, with much better ray tracing performance". Game Debate. Retrieved January 29, 2021.
  30. Allan, Darren (November 11, 2020). "AMD promises RDNA 3 GPUs will be as big a leap forward as Big Navi". TechRadar. Retrieved December 16, 2020.
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