Re: 80286 protected mode

On 2024-10-07, Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:

Here's another speculation: The 286 protected mode was what they
already had in mind when they built the 8086, but there were not
enough transistors to do it in the 8086, so they did real mode, and in
the 80286 they finally got around to it.  And the idea was (like AFAIK
in the iAPX432) to have one segment per object and per procedure,
i.e., the large memory model.  The smaller memory models were
possible, but not really intended.  The Huge memory model was
completely alien to protected mode, as was direct hardware access, as
was common on the IBM PC.  And computing with segment register
contents was also not intended.
>
If programmers had used the 8086 in the intended way, porting to
protected mode would have been easy, but the programmers used it in
other ways, and the protected mode flopped.
>
Would it have been differently if the 8086/8088 had already had
protected mode?  I think that having one segment per object would have
been too inefficient, and also that 8192 segments is not enough for
that kind of usage, given 640KB of RAM (not to mention the 16MB that
the 286 supported); and with 640KB having the segments limited to 64KB
is too restrictive for a number of applications.

I completely agree. Back when the 8086 was designed, 640K seemed like a
lot. They never expected it to grow beyond the minframes of their time.