> So you can reasonably run graphics, 10 GbE, and one NVMe device off your 3.0x16 PEG lanes
Sure but you won't find any board with a setup like that. You can also reasonably split the x4 nvme lanes into 2x x2 but again you won't find a such a setup.
You'll find no shortage of boards with everything wired up to the PCH, though, and it's "good enough" even if it isn't ideal. The extra bandwidth will certainly not be unwanted. Especially when you're also sharing that bandwidth with USB and sata connections.
> The real use-case that I see is SuperCarrier-style motherboards that have PEX/PLX switches and shitloads of x16 slots multiplexed into a few fast physical lanes, like a 7-slot board or something.
I think those use cases would instead just use threadripper or epyc. Epyc in particular with its borderline stupid 128 lanes off of the CPU.
Sure but you won't find any board with a setup like that. You can also reasonably split the x4 nvme lanes into 2x x2 but again you won't find a such a setup.
You'll find no shortage of boards with everything wired up to the PCH, though, and it's "good enough" even if it isn't ideal. The extra bandwidth will certainly not be unwanted. Especially when you're also sharing that bandwidth with USB and sata connections.
> The real use-case that I see is SuperCarrier-style motherboards that have PEX/PLX switches and shitloads of x16 slots multiplexed into a few fast physical lanes, like a 7-slot board or something.
I think those use cases would instead just use threadripper or epyc. Epyc in particular with its borderline stupid 128 lanes off of the CPU.