Compiler vendors made some workarounds via the large & huge memory models, but porting a program from a 32bit minicomputer (VAX) would prove difficult if it addressed large amounts of memory, and would require a rewrite. This became a massive headache for years as you could not easily contain more than 64kb of data at a time as you would exceed a segment. However to preserve some compatibility with the 8080 processor it was decided that the 8086 (and 8088) CPUs would work with 64kb segments. The 8086 processor could address 1MB of RAM, with its 20bit address bus.
It was this that effectively brought 32bit computing to the masses with the Compaq Deskpro. Because of the open nature of the IBM PC, clone manufacturers were able to leapfrog IBM, and release 386 based machines before IBM got around to releasing the PS/2 model 80. The 68000 however did not include any kind of memory management unit (MMU) making things like porting UNIX improbable (The SUN-1 workstation included a custom MMU). The 68000 could work with 32bit data, but it was restricted to a 16bit data bus, and only could address 24bits of RAM (16 megabytes). Lastly the 386 introduced hardware virtualization, the “v86” mode where the 386 could emulate multiple 8086 processors, allowing people to have multiple ‘virtual machines’ on the desktop.Īt the time the only consumer grade 32bit processor was the hybrid 32/16 68000 from Motorola. The 386 also included a larger memory model, the so called “flat mode” where it could directly address 4GB of combined code+data, while the 286 could address 1GB it was limited to 64kb segments. The first being a 32bit processor where it could handle larger data sizes than the 16bit 286 & 8086. The 386 brought three major changes onto the then champion processor the 286.
#COMPILING CXBX RELOADED LICENSE#
However this all changed with the 386, as Intel stopped renewing these agreements with other companies (IBM had a license that included the 386, although they were slow in making their own), so now Intel was in charge of its destiny.
Before this time, Intel had licensed their processors to other companies (Siemens, AMD, Harris, IBM etc) So that if there was some kind of production issue at Intel other companies could manufacture 8086,80186s and 80286s. This means that Intel, and only Intel would fabricate the 386 processor. The 386 microprocessor was the first CPU by Intel that was single sourced. The 386 is perhaps one of the top ten things that has changed our world, along with 4.3BSD.
Kind of interesting is that Linux has finally dropped support for the 80386 microprocessor.
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