Subj : Interrupts
To   : Lee Aroner
From : Jonathan de Boyne Pollard
Date : Mon Jun 04 2001 01:17 am

LA>> I had assumed that OS/2 used the same method of
LA>> forcing a processor exception
LA>> to jump to ring zero as MonopolySoft uses, apparently I was wrong.

JdBP>> Strictly speaking, the design of OS/2 in this area is partly
JdBP>> Microsoft's.

LA> I guess that would tell us something about what G. Letwin thought
LA> of the jump to the bios IBM copyright notice as a means of
LA> switching processor state then, eh?

That's not involved here, though.  That particular mechanism was used, in OS/2
version 1.x, for switching from protected mode back to real mode in order to
run DOS programs in the DOS box.  Here, we are talking about the CPU remaining
in protected mode, and simply switching from ring 3 to ring 0, which is what
happens when a native OS/2 program calls into the kernel.



--- FleetStreet 1.22 NR
* Origin: JdeBP's point, using Squish <yuk!> (2:257/609.3)