Ask HN: Security-first personal/mobile computing architecture?

Do efforts from Apple, as well as recent Intel/MSFT collabs, represent a security-first design philosophy for personal computing?

What would a security-first personal or mobile computer designed from the ground up look like from a high-level architectural perspective, in ways that are distinct from the status quo?

What main usability tradeoffs, if any, would result for your security-first design?

Answer can be in consideration of currently non-existent but feasible supporting technology.