Re: Byte ordering (was: Whether something is RISC or not)

David Brown <david.brown@hesbynett.no> writes:

On 04/10/2024 00:17, Lawrence D'Oliveiro wrote:

Compare this with the pain the x86 world went through, over a much longer
time, to move to 32-bit.

>
The x86 started from 8-bit roots, and increased width over time, which
is a very different path.

Still, the question is why they did the 286 (released 1982) with its
protected mode instead of adding IA-32 to the architecture, maybe at
the start with a 386SX-like package and with real-mode only, or with
the MMU in a separate chip (like the 68020/68551).

And much of the reason for it being a slow development is that the world
was held back by MS's lack of progress in using new features.  The 80386
was produced in 1986, but the MS world was firmly at 16-bit under it
gained a bit of 32-bit features with Windows 95.  (Windows NT was 32-bit
from 1993, and Win32s was from around the same time, but these were
relatively small in the market.)

At that time the market was moving much slower than nowadays.  Systems
with a 286 (and maybe even the 8088) were sold for a long time after
the 386 was introduced.  E.g., the IBM PS/1 Model 2011 was released in
1990 with a 10MHz 286, and the successor Model 2121 with a 386SX was
not introduced until 1992.  I think it's hard to blame MS for
targeting the machines that were out there.  And looking at
<https://en.wikipedia.org/wiki/Windows_2.1x>, Windows 2.1 in 1988
already was available in a Windows/386 version (but the programs were
running in virtual 8086 mode, i.e., were still 16-bit programs).

And it was not just MS who was going in that direction.  MS and IBM
worked on OS/2, and despite ambitious goals IBM insisted that the
software had to run on a 286.

The fact that the 386SX only appeared in 1988 also did not help.

- anton
--
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>