[_zoltan_]

usually it's 2-2-2 (2 GPUs, 2 NICs and 2 NVMe drivers on a PCIe complex). no NVLink here, this is just PCIe - under this PCIe switch chip there is full bandwidth, above it's usually limited BW. so for example going GPU-to-GPU over PCIe will walk

GPU -> PCIe switch -> PCIe switch (most likely the CPU, with limited bw) -> PCIe switch -> GPU

NVLink comes into the picture as a separate, 2nd link between the GPUs: if you need to do GPU-to-GPU, you can use NVLink.

you never needed to DIY your stuff, at least not for the last 10 years: most hardware vendors (Supermicro, Dell, ...) will sell you a complete system with 8 GPUs.

what's nice on GH200/GBx00/VR systems, is that you can use chip-to-chip NVLink between the CPU and GPU, so the CPU can access GPU memory coherently and vica versa.