From: wolff@zen.et.tudelft.nl (Rogier Wolff) Subject: Re: Linux and OS/2 Date: 2 Jan 1993 10:16:53 GMT
sdw@meaddata.com (Stephen Williams) writes:
>"Current Intel 386/486 series cannot nest 'Ring 0' programs in
>hardware."
>Using other terms:
>This means that a 32-bit (Ring 0, priviledged) OS (like all full
>Unixes, OS/2, Windows NT, Windows in enhanced mode) cannot run
>underneath another with simple hardware modes.
>They could run unpriviliged and have the priviliged instructions
>emulated.
Nope. The problem is that the instructions to enter/leave priviliged
mode do not fault. This means that the controlling OS doesn't knoww
wether to handle the fault by emulation or by passing it along to the
other OS.
>VM (On IBM compatible Mainframes) does this nesting, either in
>hardware or software (I don't know...).
You need basic hardware features to be able to do this nesting. Intel
forgot to look at decade old IBM designs, and forgot the necessary features.
>What the world (at least the Unix world) needs right now is a 'virtual
>386 mode', where the 386-8086 part is emulated in software. This
>would even allow a version of Unix to run under itself. This would be
>great for debugging (kernels, startup, etc.).
>All it takes is some hard work.
Nope. You need intel to correct their specs on the 386, and then
get them to replace existing 386s. Good luck.
>Note that Soft-PC and Sun-PC both emulate at least a 286 in software,
>as that is what it takes to run Windows 3.1 (unlike 3.0 which would
>run on 8086).
Yes they emulate EVERY instruction in software. What we want here is
the hardware to run the instructions, and software to handle the
"too priviliged to be done automatically" things.
>The Sun-PC 486 board even lets you run a full 32-bit application/os's with
>full vga mapped efficiently onto X windows.
This is a hardware solution which doesn't correspond with software solutions
on dos boxes.
Roger
-- **** a 486 in V86 mode is like a VW buggy with a 6 litre V12 motor. **** EMail: wolff@duteca.et.tudelft.nl ** Tel +31-15-783644 or +31-15-142371