Officially, AMD announces with great fanfare that the new generation video game consoles use its RDNA 2 graphics architecture just like the RX 6000 for PC, but from the outset there is an important omission, which is Infinity Cache, since console APUs they lack it. It’s also missing from the Steam Deck processor and Ryzen 6000 processors, which also use the same architecture. Why does AMD say this then?
It could be said that AMD has not yet found a way to implement the Infinity Cache in an APU or SoC and that although it is in the RX 6000 series (as it helps the performance of said graphics cards) it is not part of what it is. the RDNA 2 specification.
Is it true that the PS5 GPU is not RDNA 2?
We must start from the fact that the PS5 APU has been designed by AMD for SONY, which contains, on the one hand, elements unique to the console and, on the other hand, elements derived from its PC technology. What defines a graphics architecture today is the Shader unit (or Compute Unit in the case of AMD) and it can be said without problems that in this aspect the RX 6000, Xbox Series, Steam Deck and PS5 share API graph.
But this is not true as such, since there is a point where it differs and it is precisely said graphic API used. RDNA 2 on PC was designed around DirectX 12 Ultimate which is also found on Xbox, instead, PS5 uses a proprietary API with similar specifications to DX12 Ultimate. Being a closed ecosystem, we do not know which functions of the set have been implemented in the SONY console and which have not.
One that is controversial is Variable Rate Shading, whose operation requires the use of the new raster and ROPS units that RDNA 2 brings with it. SONY has never mentioned this technology when talking about its console, nor have they been seen talking of the Mesh Shaders, but of the Primitive Shaders. Both concepts serve the same purpose, but the implementation is different and AMD has abandoned the Primitive in exchange for the Mesh in RDNA 2. That is why gossips claim that the PS5 GPU is not RDNA 2 for not having the complete setbut we cannot consider it RDNA 1 either, since it has elements such as hardware ray tracing typical of the second generation.
AMD’s semi-custom business
One of the sources of business for Lisa Su’s company is the creation of custom APUs for specific customers. From AMD they offer the different pieces already developed that allow their clients to create their own design quickly. Key to this is the Infinity Fabric interconnection to intercommunicate the different blocks with each other and easily generate new designs in record time.
It must be assumed that a GPU is not just a component, but rather a very complex structure of various blocks and in the case of a video game console, what the manufacturer will be interested in is that it has a 1:1 correlation with its software and development tools. Remember that PS5 does not use the same tools, what matters to SONY is not that PS5 is RDNA 2 or not, which is only a commercial sign, but that it has all the functions that they have implemented in their graphical API, which we remember that it is not about DirectX 12, and that they believe that this generation of consoles will be useful to them.
In conclusion, the PS5 APU was created under specific specifications that SONY passed on to AMD for proprietary use. We do not know all of them and we must take into account that today the documentation of the development kit is not in the public domain. The PS4 one can be found in certain obscure places on the web and contradicts some assumptions about the console, so it is possible that when the PS5 leaks we will find ourselves in the same situation.
Therefore, the PS5 iGPU is not RDNA 2 as such, it is a modified variant for SONY and its criteria that makes use of some parts of the architecture, but does not implement the entire specification as such, so it cannot be taken as if it were the central part of the AMD architecture.