I'm not trolling here: Do you think that Marvell sells the chips wholesale buy the vendor buys the feature set (IP/drivers/whatever)? That would allow Marvell to effectively sell the same silicon but segment the market depending upon what buyers needs. Example: A buyer might need a config that is just a bunch of 50GB/s ports and another 100GB/s ports and another a mix. (I'm thinking about blowing fuses in the manuf phase, similar to what AMD and Intel do.) I write this as a complete noob in switching hardware.

You’re talking about link aggregation (LACP) here, which requires specific settings on both the switch and client machine to enable, as well as multiple ports on the client machine (in your example, multiple 50Gbps ports). So while it’s likely possible to combine 50Gbps ports like you describe, that’s not what I was referring to.

This is incorrect - they can split however the driving chip supports. (Q|O)SFP(28|56|112|+) can all be split to a single differential lane. All (Q|O)SFP(28|56|112|+) does is provide basically direct, high quality links to whatever you chips SERDES interfaces can do. It doesn't even have to be ethernet/IB data - I have a SFP module that has a SATA port lol.

There's also splitting at the module level, for example I have a PCIe card that is actually a fully self hosted 6 port 100GB switch with it's own onboard Atom management processor. The card only has 2 MPO fiber connectors - but each has 12 fibers, which each can carry 25Gbps. You need a special fiber breakout cable but you can mix anywhere between 6 100GbE ports and 24 25Gbe ports.

https://www.silicom-usa.com/pr/server-adapters/switch-on-nic...

Here’s an example of the cables I was referring to that can split a single 400Gbit QSFP56-DD port to two 200Gbit ports:

https://www.fs.com/products/101806.html

But all of this is pretty much irrelevant to my original point.