Mail Archives: djgpp/1999/09/27/12:25:10
Eli Zaretskii (eliz AT is DOT elta DOT co DOT il) wrote:
> On Wed, 22 Sep 1999, Duncan Coutts wrote:
> > DJGPP runs using DPMI which has many nice features such as memory
> > protection, virtual memory, but it is still Dos single tasking.
> There's nothing inherently single-tasking about DPMI. As a matter of
> fact, Caldera's DR-DOS already supports multi-tasking with its DPMI
> host.
It's even stronger than that: if memory serves, DPMI was invented to
allow multitasking, in the first place. DPMI was designed as the inner
core of Windows 3.x: it provided the multitasking machinery needed for
Windows to be able to support stuff like multiple simultaneous DOS
boxes in virtual machines, and the task switching between Windows
apps. In a nutshell, Windows 3.1 is a central DPMI server running
multiple clients, one of them being the GUI itself.
AFAIK, many of the limitations found in DPMI, as compared to its
predecessor VCPI, are mandated by exactly this support for
multi-tasking. It offers less control over the virtual memory hardware
and over protection levels because in multi-tasking, allowing such
control would be disastrous.
--
Hans-Bernhard Broeker (broeker AT physik DOT rwth-aachen DOT de)
Even if all the snow were burnt, ashes would remain.
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