In your opinion, if you could force power supply makers to add another voltage rail, which voltage would you pick?
Solving for the problems of higher current, lower voltage DC we use in ATX format supplies today requires higher gauge copper, but the cable run between the GPU and PSU is so shot that the cost of extra copper could very well be less than the increased cost of a higher voltage supply.
where is this typical? in my experience, typical is 200A service for residential. is mains service amps dependent on provider/region/etc?
Often, those transformers on the pole have some wiggle room in what they can deliver, and just because you upgraded from 100a to 200a service doesn’t mean you’ll actually see a real world change in usage. You usually don’t. Utility companies can over provision that capacity because not everyone on a street switches on their microwave at the same time, etc.
Does the old way of building PCIe cards still make sense when the GPU now draws more power than all of the other system components combined? GPU sag (i.e. the card weighs so damn much) is such an issue that one manufacturer actually put a level in their card.[0] The 4090 probably needs three slots just to keep it attached to the motherboard.
When someone buys a desktop these days, it's very often because they need a discrete GPU. You buy a dedicated desktop GPU because the thermal envelope of a laptop can't support a card that would draw 600W - even if it were possible to shrink the card into a laptop (or make the laptop big enough to fit the 600W card). The top of the line Intel processors draw in the neighborhood of 150W but that doesn't necessitate going to a different form factor. Future motherboard and south bridge designs should mount the GPU independently of the other components.
[0] https://www.tomshardware.com/news/geforce-rtx-4090-has-a-spi...