AMD’s Navi 4C “RDNA 4” MCM GPUs are said to have powered the next-generation Radeon RX 8000 enthusiast graphics cards. We recently heard rumours that AMD had cancelled their high-end RDNA 4 GPUs. Moore’s Law is Dead appears to have some additional information on a specific SKU that was supposed to be part of the next GPU range but was axed in favour of more mainstream GPUs.
MLID has provided an alleged diagram of a Navi 4C GPU, which was to be one of three Navi 4 configurations based on the RDNA 4 architecture, the other two being the Navi 4X and Navi 4M, as revealed by Kepler_L2 a few months ago. The Navi 4C layout appears to be a fairly advanced MCM architecture that made use of a variety of building pieces.
The package substrate that would store numerous AIDs and MIDs on top of the AMD Navi 4C (RDNA 4) GPU’s base layer.
The AID is an active interposer die, and there are four of them, along with a single MID or Multimedia & I/O die that was supposed to be identical to the MCD found on the existing Navi 31 and Navi 32 MCM GPUs.
This chiplet included VRAM bus controllers and the Infinity Cache, as well as other multimedia features. The MID was linked to the AID by a next-generation interconnect fabric, and the AIDs were linked to one another via the same fabric.
Few more codenames 🙂
— Kepler (@Kepler_L2) April 18, 2023
Navi4X
Navi4M
Navi4C
MI400 Mercury/Venus/Earth
Each AID now had three SEDs piled on top in a stacked chiplet layout. These SEDs were the primary GPU IP blocks in charge of shader tasks. According to the diagram, this Navi 4C setup based on the RDNA 4 graphics architecture included at least 9 SEDs.
The entire package was built on TSMC’s COW-V TSV technology and was supposed to have many configurations, but because we don’t know the specific configuration or CU/WGP architecture of RDNA 4, it’s too early to speculate on what this chip could’ve been used for.
According to the leaker, this specific configuration was expected to be featured on the AMD Radeon RX 8900 XTX, which should’ve been an ultra-enthusiast product since it replaced the 7900 XTX, but that doesn’t appear to be the case anymore, and the chiplet design of such a scale isn’t ready at least for the RDNA 4 generation of GPUs. The business most likely did not fulfil its aims or expectations with the RDNA 3 series and went back to the drawing board to get things right for future MCM designs.
While this is still a rumour and nothing has been formally confirmed by AMD, the RDNA 4 lineup appears to only include Navi 44 and Navi 43 SKUs, leaving the Navi 42 and Navi 41 chips out of the picture.
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