Earlier quoted context omitted.
> In a universe where you want high-performance energy efficient RAM [.....] You simply can’t have this with socketed RAM. You make it sound like a prerequisite. I'm pretty sure the reason LPDDR is Low Power is not due to (currently) being unavailable in socketed modules - that would seem to be a side-effect of the original target market (smart phones). They are just some BGA packages, I see no reason they couldn't b…
I've never done anything beyond amateur electronics, so sorry if I'm way off base here, but it at least seems intuitively plausible to me that soldering the components to the board allows them to work reliably at lower power. With a pin and socket connection, you've got to try and be at least reasonably resistant to corrosion or other sources of less-than-perfect connection. That said, I don't know that RAM chips are…
If you design to a socketed DIMM package, you actually have two trace domains, the CPU to the socket, and the socket to the RAM chips. For that to be reliable, you have to adhere to standards for DIMM (or SODIMM) so that multiple manufacturers can build compliant interchangeable parts.
If you solder the chips down to the main board directly, you only have once domain for the traces, CPU directly to RAM. At that point you can tweak the design for several goals, speed, power, etc.. And you can tune the drive strength on the signalling the same.
That is how you end up with more efficient soldered designs over socketed designs.