They had to make some Gen 5-capable custom adapters that plugged into one of the front-of-chassis NVMe bay connectors (thus disabling that bank of 4 drive bays), and then routed that signal all the way back to the rear, using Nvidia's custom edge plug on the card.

Normally, if you're deploying the 800 Gbps ConnectX-8 cards, you have the card in one slot, then a little adapter board right next to it, with a cable NVIDIA makes. But for this, it had to be fully custom.

Would be neat to hear more from STH how that cable was made exactly, because it seems like hand-building PCIe cables can be a bit tricky!