SLI has been dead for a while now and Nviida recommends you use a single power graphics card rather than 2 mid-range ones. Game developers have stopped optimization for multiple graphics cards and the NVLink is gone too. Now P2P communication support for the Nvidia RTX 4090 has been dropped as well.
No Peer-To-Peer Communication Support On The RTX 4090
User vasilii.shelkov posted an issue on the Nviida developers forum and mentioned that some standard Nvidia tests fail when using a pair of RTX 4090 graphics cards. He shared the results of his tests and noted that when the GPUs were checked for peer to peer memory access he would get the following prompt:
“Peer access from NVIDIA GeForce RTX 4090 (GPU0) → NVIDIA GeForce RTX 4090 (GPU1) : Yes
Peer access from NVIDIA GeForce RTX 4090 (GPU1) → NVIDIA GeForce RTX 4090 (GPU0) : Yes
Enabling peer access between GPU0 and GPU1…”
But then peer access would be disabled and the test would fail. One of the support staff reported that peer-to-peer support is not available in the RTX 4090. He mentioned that there was an error in the driver or application and that the dual RTX 4090 configured system should not be reported as peer-to-peer compatible. He went to on say that the reporting is being fixed and that future reports will instead show:
I. # ./simpleP2P
[./simpleP2P] – Starting…
Checking for multiple GPUs…
CUDA-capable device count: 2
Checking GPU(s) for support of peer to peer memory access…
/> Peer access from NVIDIA GeForce RTX 4090 (GPU0) → NVIDIA GeForce RTX 4090 (GPU1) : No
/> Peer access from NVIDIA GeForce RTX 4090 (GPU1) → NVIDIA GeForce RTX 4090 (GPU0) : No
Two or more GPUs with Peer-to-Peer access capability are required for ./simpleP2P.
Peer to Peer access is not available amongst GPUs in the system, waiving test.
Device 1 is not peer capable with some other selected peers, skipping
Step 0 done
Process 0: verifying…
Process 0 complete!
While there is no confirmation, it is safe to assume that other cards such as the RTX 4080, 4070, and 4060 do not have this functionality either. While we do not know for sure why this feature is not supported on such a high-end card, it could be because Nvidia is looking to sell its L6000 graphics cards.
Let us know what you think about the Nvidia RTX 4090 not supporting P2P communication. If you are interested in getting one then you can check out our recommended RTX 4090 graphics cards.