[bradfa]

Going to only 12V power to the motherboard doesn't actually make them much more complicated, or any more complicated really. Like half of a modern motherboard design today is just power supplies anyways, as all CPUs will do voltage scaling to save power. It's not like your CPU takes 3.3V input directly, most are running in the 0.8-1.5V range, even DDR4 is 1.2V, and the CPU is the majority of the consumption on the actual motherboard (high power graphics cards usually have their own 12V input connector, the PCIe edge cannot transfer enough).

[dicknuckle]

I expect motherboards could be more reliable if there was a standard 12v to 5v, 3.3v, 1.5v etc pluggable converter that they all used. It could cut down on E waste. Instead of having to discard an entire motherboard, the low voltage converter board could be swapped out and repaired/discarded. The same companies that make ATX power supplies could also make the discreet low voltage converters. ATX innards could be smaller, less wiring between components.

No that's silly, we should continue to use a design from 1995, itself replacing a design from 1981.

[bradfa]

Well, sure that'd be nice, but it would add quite a lot of cost. High current carrying connectors are not free.

You can buy a nice AMD Ryzen motherboard for like $80 retail (Newegg shows $59 is where new unopened ones start). Normal electronics supply chain and shipping margins means it cost roughly half that to manufacture it. So on a $40 bill of materials and labor cost if you add even just $1 to make something better/modular/whatever then you're adding a significant amount in terms of percentage cost increase.

As much as reducing electronics waste is a worthy goal, the economics of it aren't aligned quite yet in today's world.