I think the future of microkernels is the L4 family: http://en.wikipedia.org/wiki/L4_kernel http://en.wikipedia.org/wiki/L4_kernel L4 systems are much smaller

I think the future of microkernels is the L4 family: http://en.wikipedia.org/wiki/L4_kernel http://en.wikipedia.org/wiki/L4_kernel L4 systems are much smaller and simpler than Mach: (7 system calls and a footprint of 12k, compared to 140/330k for Mach, according to Wikipedia). L4 has much better IPC performance. It appears that some people attempted to port Hurd to L4 but gave up: http://www.gnu.org/software/hurd/history/port_to_l4.html http://www.gnu.org/software/hurd/history/port_to_l4.html In that page they say "Eventually, a straight-forward port of the original Hurd's design wasn't deemed feasible anymore by the developers, partly due to them not cosidering L4 suitable for implementing a general-purpose operating system on top of it, and because of deficiencies in the original Hurd's design, which they discovered along their way." There is no reference or explanation of why they considered L4 unsuitable for a general-purpose operating system, which is too bad, because it would be extremely interesting to read.