6 Aug
2025
6 Aug
'25
5:36 p.m.
On Wed, Aug 06, 2025 at 05:45:12PM -0400, Murray McCullough via cctalk wrote:
40 years ago this year Intel came out with the 80386 –
386 – or i386.
Also iAPX 386, a name that nobody but Intel's marketing department paid any
attention to.
Either seems to be correct. What this meant was a
memory address of 4GB,
far beyond what an average computer user would need or want, but was so
much more than previously(8086, 80286); ‘true’ multi-tasking which for the
average computer user didn’t mean all that much; and paging, which made
virtualization possible- experimenters were over-joyed!
The 80286 introduced protected mode, which is sufficient to implement a
proper operating system, since protected mode enables sandboxing user
processes in a virtual memory environment. We know this because Andrew
Tanenbaum did just that: MINIX 2 will run on your old 286 and give you
something broadly resembling mid-1980s Unix.
Unfortunately, putting the 286 into protected mode cratered performance as
it would then need to reload the base-and-bounds from memory every time a
segment register was reloaded. Since the 286 basically only had two
general-purpose segment registers, these reloads were extremely common.
Also, real-mode code cannot be reliably made to run in 286 protected mode.
so not only is multitasking noticably slower even when running just one
program, but if that one program you want to run is for MS-DOS, it's not
going to run at all.