DOS has direct access to the PC's hardware (DOS is the Operating System),
current versions of Windows is the OS (like XP, which is based on Windows NT
technology) and prevent programs from having direct control over the
hardware. Apps must now communicate thru Windows which creates a certain
amount of overhead and adds stability.

JS

I need examples of what you think is "slow".  I haven't seen that here,
but I don't run the same things that you do.

In 2K and XP, Windows has a process called NTVDM, which creates a
virtual DOS machine on your PC.  It's not DOS -- it's a sophisticated
DOS emulator.  Sophisticated enough, in fact, that I haven't found much
that *won't* run under it.

The big problem children are DOS games.  Early DOS PCs were slow and
limited.  (The *original* IBM PC had an 8088 CPU running at 4.77 mhz.
My old PC clone running DOS used a NEC V20 CPU running at a whopping 10
mhz. That's *megahertz*, not *gigahertz*.)

To get acceptable performance for games and the like, programmers would
bypass DOS and access the hardware directly.  That was fine in DOS,
which was a single-tasking system doing one thing at a time.  It was
*not* fine when Windows came along, with the ability to run moe than one
program at a time.  A program could not assume it owned the machine, but
needed to cooperate with other programs and take it's turn at getting
resources.

Microsoft created Direct X as a response to the needs of game designers
accustomed to writing directly to the hardware, and provided an API
they could use in their games to get the access to the hardware without
causing problems for everything *else* running.

My old DOS programs run at least as fast in an XP NTVDM as they did on
my old machine, but I'm mostly using character mode apps.  I'm not
trying to play DOS games, with the exception of a few oldies like the
DOS ports of VMS Empire, or Unix Larn.

What do you see as slow?

______
Dennis