[ohazi]

> Is there anyone shipping an ARM motherboard and ARM chip? I think the "openness" is also defined by what the market offers. All I see are non-extendable notebooks.

Pretty much all ARM application processors use soldered BGA packages over sockets, and there also isn't the same tradition of defining a standard pinout for a generation or two (or five) of chips like there has been for x86 (e.g. LGA1151, AM4, etc.).

You can't really design a motherboard without this, so each design tends to have a custom breakout board or carrier card that's designed to be used in relatively specific installations.