Re: 40Gbps sounds amazing, but...
There's no market for anything faster than 1Gbps but slower than "the fastest feasible"
Datacentre needs the fastest you can give it, but home and office usage is almost always practically limited by the Internet connection, which is currently almost always in the region of 40-500Mbps, and basically never faster than 1Gbps.
Dunno if that was solved for 10
As they're actually fallback symbol rates of 10Gbps, why sell at 2.5Gbps when you can sell it as 10Gbps
Power delivery adds further complexity, I know the 2-wire Ethernet standards committees are currently trying to figure out how to do that. Dunno if that's solved for 10/5/2.5Gbps though.
So, what are you going to do with 5Gbps?
Biting the hand that feeds IT
