EAX: Contains hi-res mode number to set (may be a VESA or non-VESA mode).
EBX: Contains the VM handle (always the currently executing VM).
EBP: Points to the Windows VM's Client Registers.
Save everything that you use. CY returned means that the mini-VDD handled the call. NC returned indicates that the mini-VDD did not handle the call.
This routine is called by the VESA/hi-res restore routine in the Main VDD when the user switches back to a full screen VESA/hi-res mode VM. If you are only interested in being able to restore VESA standard hi-res modes, then you do not need to implement this function since the Main VDD will call Interrupt 10h Function 4F02h in order to set the VESA mode number. You should only implement this function if you are going to save/restore chipset specific modes that are not VESA modes.
If the mode number passed in EAX is a VESA mode number, you should return NC and let the Main VDD set the mode. If the mode number passed in EAX is a non-VESA hi-res mode that is particular to your card, if possible, this function should not touch VRAM since this could cause page faults and confuse the register state of the mode set. In other words, try not to erase the screen during the mode set if possible.