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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: the 286, Byte ordering
Date: Sun, 5 Jan 2025 02:56:08 -0000 (UTC)
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According to Anton Ertl <anton@mips.complang.tuwien.ac.at>:
>antispam@fricas.org (Waldek Hebisch) writes:
>>From my point of view main drawbacks of 286 is poor support for
>>large arrays and problem for Lisp-like system which have a lot
>>of small data structures and traverse then via pointers.
>
>Yes.  In the first case the segments are too small, in the latter case
>there are too few segments (if you have one segment per object).

Intel clearly had some strong opinions about how people would program
the 286, which turned out to bear almost no relation to the way we
actually wanted to program it.

Some of the stuff they did was just perverse, like putting flag
bits in the low part of the segment number rather than the high
bit.  If you had objects bigger than 64K, you had to shift
the segment number three bits to the left when computing
addresses.

They also apparently didn't expect people to switch segments much.
If you loaded a segment register with the value it already contained,
it still fetched all of the stuff from memory.  How many gates would
it have taken to check for the same value and bypass the loads?  If
they had done that, we could have used large model calls everywhere
since long and short calls would be about the same speed, and not
had to screw around deciding what was a long call and what was short
and writing glue codes to allow both kinds.

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly