I know that backplanes (like the old S100 from the 1980s) hit certain performance walls, but they are more adaptable than motherboards. You could swap out any

I know that backplanes (like the old S100 from the 1980s) hit certain performance walls, but they are more adaptable than motherboards. You could swap out any component including the CPU and even the various interfaces. It's nice that single board computers like the Raspberry Pi use so little power, but they are still monolithic and impossible to upgrade. I wish somebody would make a newer, faster backplane-like form-factor for small computers. The RPi Compute Module is an interesting step in that direction, though it would be better if the RAM was on a separate card.