paging:

The second article in the "PORTING UNIX TO THE 386" series discussed the utilities we had to build to test the port on an actual 80386 PC.
By far, the most popular article.

Once the system is debugged and tested, the next step was to load on more code to expand with. So we moved "tar balls" to the swap space with this utility to provide a primative file upload capability.

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.

The 386BSD specification was in two parts - one that detailed getting to a operational system that could build itself and basic console applications, and a more extensive community involvement part, called "A Modest Proposal".

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.

The 386 Paging Memory Management allocates memory in 4KB and 4MB allocation units. This impacts the way programs execute and share file data.

386BSD started out in 1989 with a derivative virtual memory system from the VAX by way of a 68030. In February/March 1991, it was cutover to a totally different one cut out of CMU's MACH system, and released with Net/2.

Support the processor, and support the ISA bus peripherals are the objectives for the first parts of 386BSD.

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

We coded trap handlers and simulated read and write faults to test out page faults with our processor support code. On a 2MB machine, we knew we'd get 1,000's.