interrupt control:

This, the first article, is the first published mention of 386BSD. By this time, the project had been operational for 18 months, and William Jolitz was at Berkeley working on the Net/2 release.
In this installment, we discussed the beginning of our project and the initial framework that guided our efforts, in particular, the development of the 386BSD specification.

This article, last of the original three done altogether in 1990, on getting the critical pieces functioning independantly that we needed to do the port. Once these we obtained, the kernel was inevitable.

We didn't just load and debug the kernel; we chose to prove portions first. That way we learned the dependances first, and could try alternatives seperately. Later we used the same means to revise them later.

We coded specialized trap handlers for interrupt traps, as these were initimate with the systems interrupt control hardware, not part of the processor.