[z4y5f3]

NVLink advertises combined bandwidth in both direction, so the 1800 GBps NVLink on Blackwell is actually 900 GBps for everyone else. PCIe can also do multi-node direct transfer via PCIe switches and has been already widely adopted. NVLink still has the power and chip arena advantage even if the bandwidth is similar.

[touisteur]

I was just saying they've announced x2 already, around the same pace as PCIe. And it's G-Byte-ps on nvlink, while G-bit-ps on PCIe, right? I'm probably missing something...

Anyway, good read here https://community.fs.com/article/an-overview-of-nvidia-nvlin...

[nsteel]

Both the PCIe and NVLink numbers here are full-duplex bandwidth. So no, you're not missing anything, you are correct. NVLink 5.0 is far ahead (but presumably it's not actually shipping yet either). Next-gen PCIe 7.0 512GB/sec full-duplex bandwidth actually sits between NVLink 2.0 (300GB/sec) and NVLink 3.0 (600GB/sec).

NVLink 5.0's 1800GB/sec comes from 18 NVLinks, with each NVLink comprised of 2 lanes of 200Gbps (single-duplex). So in normal single-duplex numbers, each NVLink is 400Gbps, and 18 links together provide 7200Gbps. When advertised as full-duplex bandwidth that's 14400Gbps (or 1800GB/sec).

In comparison, PCIe 7.0 uses only 128Gbps lanes: 128Gbps x 16 lanes x 2 directions = 4096Gbps (or 512GB/sec).

PCIe has always been way behind cutting-edge serdes speeds. NVidia just made it more obvious to those working outside of specialist HPC and Networking. But we must cut PCIe some major slack, it has to (eventually) work on relatively cheapo hardware from hundreds of different vendors, in a restricted power and thermal environment i.e. consumer devices.

[touisteur]

Ah thanks for the detailed breakdown. You're right that PCIe has more problems to deal with.