16th February 00:19
Getting into Protected Mode
DPMI and VCPI will both allow you to run a program in PM starting from
VM. Typically, DPMI runs your program at PL3, and VCPI at PL0. Which
you use depends upon various factors. If you don't need to modify
resources available at PL0 only, then by all means use DPMI -- it's
significantly easier to use. For another DPMI host which provides DPMI
1.0 services, see http://www.sudleyplace.com/dpmione/.
If you choose to use VCPI, be sure to remember not to return to VM
directly (however tempting that might be). You must go through the VCPI
host to accomplish that transition.
Although it's not for the faint of heart, there is a third method to
transfer from VM to PM: the Windows Paging Import Specification. This
is the mechanism by which Windows gains control from the VM host in
order to run itself in PM. The spec describes how the VM host is called
and returns in RM, and inversely (when Windows exits), how the VM host
is called in RM and should return in VM.
Bob Smith -- email@example.com
To reply to me directly, delete "despam".