JMT ADT-F36B-F37B-D8S PCI-e 4.0 X16 to X8 X8 MCIO Bifurcation Adapter Riser Card 256G/bps Split Extender SFF-TA-1016 with Power Cable (100cm)

Great quality, and works well. Not much else to say.

For some reason these use a SATA power adapter with very thin wires rather than a standard PCIe 2x3 pin power connector. It looks like the footprint is there on the board, why not just install them?

The PCI slot card does NOT clear heat pipes that are present on threadripper (and possibly other) motherboards like the Asrock wrx90. I have large GPUs accommodate the pipes just fine, but this card is nearly flush with the motherboard near the back panel. I needed to shuffle my slot assignments around to accommodate this specific quirk. Further more it uses sata for power which is problematic as sata only delivers 50w or so by spec but the PCI slot may need up to 75 by spec. This can cause the cable/connector to burn out. The actual product works but for any serious riser install I would not risk using this simply due to the sata power.

Works great! I'm using these for an AI/LLM rig for external GPUs and bought a pair, so taking 2x PCIe 4.0 X16 slots into 4x PCIe 4.0 X8 external slots which is still more than enough bandwidth for my purposes. Just make sure your board supports 8x8x bifurcation!