Re: 80286 protected mode

On Mon, 07 Oct 2024 07:33:14 GMT, Anton Ertl 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.

Nah. Intel were never capable of thinking that far ahead. Each bodge to
the x80/x86 line was made just to take the product one step further,
without regard to any future growth. The 8086/8088 was designed to make it
easy to port across 8080/8085 code, with the segment registers tacked on
to give you a bit more address space if you needed it, if you could figure
out how to use it -- that was their idea of “technological progress”.

And then the next step was to add this new-fangled “hardware memory
protection” that the folks using the Big Computers were always going on
about, so they bodged the 8086 segmentation scheme into kind of a memory-
management scheme in the 80286.

Finally, in the 80386, they gave everybody the large, linear address space
they had been crying out for. That is, everybody who wasn’t already using
more sensibly-designed chips from companies like Motorola, NatSemi and the
RISC vendors.