[comp.sys.ibm.pc.misc] How does 386 DOS deal with 8086 binaries?

kak@sequent.uucp (Keith Kelleman) (01/08/91)

I have some questions about DOS on the 386:

Does it run in 386 native mode or 8086 emulation mode?

Is virtual 8086 mode used by DOS on the 386
i.e. to execute old XT and AT binaries?

or must all executables use the 386 instruction set?


I guess the same questions apply to the DOS
multi-tasking products like Desqview.

Thanks in advance!
Keith A. Kelleman

md@sco.COM (Michael Davidson) (01/11/91)

In article <49932@sequent.UUCP> kak@sequent.uucp (Keith Kelleman) writes:
>
>I have some questions about DOS on the 386:
>Does it run in 386 native mode or 8086 emulation mode?

If you mean MSDOS from Microsoft, then the answer is that
it runs on 80386 machines the same way that it runs on
8086 and 80286 machines - it runs in 8086 real-mode.

>Is virtual 8086 mode used by DOS on the 386
>i.e. to execute old XT and AT binaries?
>or must all executables use the 386 instruction set?

Quite the reverse - everything is assumed to be 8086
real-mode. If an application is smart enough to figure
out that it is running on a 386 and to take advantage of
it then, of course, there is nothing that DOS can do
to stop it, but you have to be in either real-mode or
virtual 8086 mode to actually make use of any DOS
system services.