CauseWay runs applications at privilege level 3. Privilege level 0 reserved instructions will cause a general protection fault (GPF). CauseWay emulates the four instructions MOV EAX,CR0; MOV CR0,EAX; MOV EAX,CR3; and MOV CR3,EAX in the GPF handler so that they may be used by an application.
CauseWay will match a DPMI 0A00h function call with target string RATIONAL/4G. This in conjunction with CR0 emulation allows support of floating point emulation by an exception handler. Watcom uses this approach under DOS/4GW operation if the floating point emulation library is not linked in. Note that this routine does not work for either CauseWay or DOS/4GW under a DPMI host such as Windows or OS/2.
Go to Table of Contents