virtual address:

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.

Most popular microprocessors use either segmentation or paging to manage memory address space access. The 386 is rare in that it possesses both. In fact, since segmentation, (see Figure 3(a)), is placed on top of paging (see Figure 3(b)), you are expected to use segmentation in some form any time memory is paged. And, most important, BSD relies on paging.

Reconciling segmentation to UNIX has never been easy, and with 386BSD its an even greater chore. The issues of supporting X86 segments in a Berkeley UNIX world.

386BSD ignored as much as possible the segmentation hardware of the x86, preferring to use a "flat" address space.

386BSD executed programs with a virtual address similar to a VAX running UNIX. In February 1991, this changed so that the format of the process virtual address space memory usage could be arranged differently.

A UNIX legacy, the "u." or per-process data structure, which held the kernel-related data of a process, was present on 386BSD prior to February 1991.

We initialized the processor with initial descriptor and page tables - one needs to run with the tables before activating memory/interrupt kernel functions.