Yes you are right, it seems M.2 M key would be providing enough bandwidth through PCIE 2.0 4X, I probably read “bits” instead of “bytes” in PCIE specs tables.
After having explored this option:
- I found some PCIE 3.0 4x 10Gbe SFP+ cards on the market, and slotting them through a “riser” cable in a PCIE 2.0 4x M.2 M key should be OK,
- I found some M.2 M key to PCIE 3.0 4x riser cables, but it seems they need an additional 12V power source. Most of them would have it plug through 4 male pins simple connector.
Would you have any M.2 M key riser cables to PCIE 4x, 8x or 16x to recommend?
Would it be possible to give the riser cable PCIE connector some power from the “SATA III power” connectors on the Odyssey (as I can’t find any other integrated power source, others single pins from GPIO connectors and so on the board only provide 3.3 or 5V) ? If so, what kind of cable could I use ?
I have seen an entry in Wiki with a walkthrough to connect a PCIE 16x GPU, and the riser cable is powered through a DIY 12V transformer source, but this seems way too much dirty to me (+ needs an additional power supply), so I would prefer using “SATA III power” connectors on board if possible.