[creshal]

From what I understand, Sun made their Doors concept public in 1993 and shipped a SpringOS beta with it in 1994, before BeOS released, but it's hard to tell if Sun inspired BeOS, or of this was a natural solution to a common problem that both teams ran into at the same time.

[p_l]

I'd expect convergent evolution - both BeOS team and Spring team were very well aware of issues with Mach (which nearly single-handedly coined the idea that microkernels are slow and bad) and worked to design better IPC mechanisms.

Sharing of scheduler slice is an even older idea, AFAIK, and technically something already done whenever you call a kernel (it's not a context switch to a separate process, it's a switch to different address space but running in the same scheduler thread)