Re: is Vax addressing sane today

In article <2024Oct5.191047@mips.complang.tuwien.ac.at>,
anton@mips.complang.tuwien.ac.at (Anton Ertl) wrote:

OK, "designed to run MS-DOS, and later Windows"?

 
The 286 protected mode was certainly not designed for MS-DOS, and
the 386 paging of linear addresses was certainly not designed for
DOS, either.

I see where I'm going wrong: I'm trying to talk about the machines
designed to run MS-DOS and later Windows, not just the CPUs. The vast
range of hardware that all had substantial degrees of compatibility as
regards booting, busses and so on. Those things let their manufacturers
compete for the DOS and Windows market, whereas x86-based machines that
weren't PC-compatible only succeeded in quite specialised niches.

Those hardware suppliers did not close off access to the more advanced
features of i386 onwards, because they had no reason to, and that let
Linux take advantage of all that hardware when it came along. That's the
point I was failing to make.

And the success of IA-32 and then AMD64 at replacing the RISCs is
exactly because it was not some DOS-centric architecture, but also
provided features needed by other OSs like 386/ix (later Interactive
Unix, which I used myself in 1990 or so), Xenix, Linux, Windows NT,
Solaris, the various BSDs, and others.  And the computers built
around these CPUs also provided these features.

Just so.

It seems to me that the 286 protected mode was a continuation of the
iAPX432 ideas, which predated DOS,

Not sure about that: it is also a bit like the base-limit memory
protection of various old mainframe architectures, done in the context of
x86 64KB segments.

and that the 386 paging imitated the virtual-memory mainstream
of bigger computing platforms at the time, such as the VAX and
S/370.

Absolutely.

John