Again, you are conflating minix and minix3. Minix3 was never in a lab to outgrow it. It is a new system, developed quite quickly and quite recently. And yes,

Again, you are conflating minix and minix3. Minix3 was never in a lab to outgrow it. It is a new system, developed quite quickly and quite recently. And yes, it is significantly better than linux. Why do you think the device IO calls shouldn't be there? Messaging primitives are present, those calls use them. They are just wrapped in a library for you, like it says right on that page. The "kernel interface" is exposing a unix like API. If you want to send arbitrary messages then you use the low level messaging API. L4 is not a kernel, it is a family of kernels. You can't run L4 any more than you can run BSD. You have to pick an actual specific implementation. Some L4 kernels are "battle tested" and some are learning projects made by single individuals and never used for anything else.