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If MI350 employs CDNA, which is based on the VEGA (GCN) architecture, does that imply that MI400, when introduced next year, will skip the 2020 GCN and directly

If MI350 employs CDNA, which is based on the VEGA (GCN) architecture, does that imply that MI400, when introduced next year, will skip the 2020 GCN and directly transition to RDNA 5 equivalent?

pella 1y ago
2026 - MI400X - CDNA 5 - UALink/IF - Helios - HBM Bandwidth: 1,400 TB/s https://www.tomshardware.com/pc-components/gpus/amd-says-instinct-mi400x-gpu-is-10x-faster-than-mi300x-will-power-helios-rack-scale-system-with-epyc-venice-cpus https://www.tomshardware.com/pc-components/gpus/amd-says-ins...
almostgotcaught 1y ago
it's all just called gcn now https://llvm.org/docs/AMDGPUUsage.html#id38 https://llvm.org/docs/AMDGPUUsage.html#id38
- adrian_b 1y ago
  The identification of the AMD GPU architectures has always been extremely confusing, with tons of different names meaning the same thing and with some names, like GCN, used for several very different things. The table linked by you is good for revealing the meaning of a part of the many AMD code names.
rfv6723 1y ago
RDNA is a dead-end. AMD went down the wrong path by focusing on traditional rendering instead of machine learning. I think future AMD consumer GPUs would go back to GCN.
adrian_b 1y ago
There will be no RDNA 5, but a unified UDNA, replacing both CDNA and RDNA. AMD has not disclosed how they will achieve the unification, but it is far more likely that the unified architecture will be an evolution of CDNA 4, i.e. an evolution of the old GCN, than an evolution of RDNA, because basing the unified architecture on CDNA/GCN, will create less problems in software porting than basing it on RDNA 4 or 3. The unified architecture will probably take some features from RDNA only when they are hard to emulate on CDNA. While the first generation of RDNA has been acclaimed for having a good performance increase in games over the previous GCN-based Vega, it is not clear how much of that performance increase was due to RDNA being better for games and how much to the fact that the first RDNA GPUs happened to have double-width vector pipelines in comparison with the previous GCN GPUs, thus double throughput per clock cycle and per CU (32 FP32 operations/cycle vs. 16 FP32 operations/cycle). It is possible that RDNA was not really a better architecture, but omitting some of the hardware that was rarely used in games from GCN allowed the implementation of the wider pipelines that were more useful for games. So RDNA was a better compromise for the technology available at that time, not necessarily better in other circumstances.
- trynumber9 1y ago
  I heard the opposite. The next is gfx13 and that it is more like RDNA with more bolted on. Which makes sense given the version numbers. MI350 is still gfx943 or gfx950. RX 9070 XT is gfx1201.

If MI350 employs CDNA, which is based on the VEGA (GCN) architecture, does that imply that MI400, when introduced next year, will skip the 2020 GCN and directly transition to RDNA 5 equivalent?

pella 1y ago

2026 - MI400X - CDNA 5 - UALink/IF - Helios - HBM Bandwidth: 1,400 TB/s https://www.tomshardware.com/pc-components/gpus/amd-says-instinct-mi400x-gpu-is-10x-faster-than-mi300x-will-power-helios-rack-scale-system-with-epyc-venice-cpus https://www.tomshardware.com/pc-components/gpus/amd-says-ins...

almostgotcaught 1y ago

it's all just called gcn now https://llvm.org/docs/AMDGPUUsage.html#id38 https://llvm.org/docs/AMDGPUUsage.html#id38

adrian_b 1y ago
The identification of the AMD GPU architectures has always been extremely confusing, with tons of different names meaning the same thing and with some names, like GCN, used for several very different things. The table linked by you is good for revealing the meaning of a part of the many AMD code names.

rfv6723 1y ago

RDNA is a dead-end. AMD went down the wrong path by focusing on traditional rendering instead of machine learning. I think future AMD consumer GPUs would go back to GCN.

adrian_b 1y ago

There will be no RDNA 5, but a unified UDNA, replacing both CDNA and RDNA. AMD has not disclosed how they will achieve the unification, but it is far more likely that the unified architecture will be an evolution of CDNA 4, i.e. an evolution of the old GCN, than an evolution of RDNA, because basing the unified architecture on CDNA/GCN, will create less problems in software porting than basing it on RDNA 4 or 3. The unified architecture will probably take some features from RDNA only when they are hard to emulate on CDNA. While the first generation of RDNA has been acclaimed for having a good performance increase in games over the previous GCN-based Vega, it is not clear how much of that performance increase was due to RDNA being better for games and how much to the fact that the first RDNA GPUs happened to have double-width vector pipelines in comparison with the previous GCN GPUs, thus double throughput per clock cycle and per CU (32 FP32 operations/cycle vs. 16 FP32 operations/cycle). It is possible that RDNA was not really a better architecture, but omitting some of the hardware that was rarely used in games from GCN allowed the implementation of the wider pipelines that were more useful for games. So RDNA was a better compromise for the technology available at that time, not necessarily better in other circumstances.

trynumber9 1y ago
I heard the opposite. The next is gfx13 and that it is more like RDNA with more bolted on. Which makes sense given the version numbers. MI350 is still gfx943 or gfx950. RX 9070 XT is gfx1201.