; Example how to temporary modify video BIOS and enable high resolution modes on my NVIDIA GeForce 9600 GSO 512

                org     100h

Start:          cli
                call    ChipsetOpen
                mov     ax,0xC000
                mov     fs,ax
                mov     word [fs:4695h],0xC3F8  ;clc / ret - all modes as valid for this monitor
                call    ChipsetClose
                sti
                ret

ChipsetOpen:    mov     ecx,0xC0010010
                rdmsr
                mov     [xC0010010+0],eax
                mov     [xC0010010+4],edx
                or      eax,80000h
                wrmsr
                mov     ecx,268h
                rdmsr
                mov     [xC000+0],eax
                mov     [xC000+4],edx
                inc     ecx
                rdmsr
                mov     [xC800+0],eax
                mov     [xC800+4],edx
                inc     ecx
                rdmsr
                mov     [xD000+0],eax
                mov     [xD000+4],edx
                inc     ecx
                rdmsr
                mov     [xD800+0],eax
                mov     [xD800+4],edx
                inc     ecx
                rdmsr
                mov     [xE000+0],eax
                mov     [xE000+4],edx
                inc     ecx
                rdmsr
                mov     [xE800+0],eax
                mov     [xE800+4],edx
                inc     ecx
                rdmsr
                mov     [xF000+0],eax
                mov     [xF000+4],edx
                inc     ecx
                rdmsr
                mov     [xF800+0],eax
                mov     [xF800+4],edx

                mov     ecx,268h
                mov     eax,18181818h
                mov     edx,eax
                wrmsr                   ; C000-C7FF
                inc     ecx
                wrmsr                   ; C800-CFFF
                inc     ecx
                wrmsr                   ; D000-D7FF
                inc     ecx
                wrmsr                   ; D800-DFFF
                inc     ecx
                wrmsr                   ; E000-E7FF
                inc     ecx
                wrmsr                   ; E800-EFFF
                inc     ecx
                wrmsr                   ; F000-F7FF
                inc     ecx
                wrmsr                   ; F800-FFFF
                ret

ChipsetClose:   mov     ecx,268h
                mov     eax,[xC000+0]
                mov     edx,[xC000+4]
                wrmsr
                inc     ecx
                mov     eax,[xC800+0]
                mov     edx,[xC800+4]
                wrmsr
                inc     ecx
                mov     eax,[xD000+0]
                mov     edx,[xD000+4]
                wrmsr
                inc     ecx
                mov     eax,[xD800+0]
                mov     edx,[xD800+4]
                wrmsr
                inc     ecx
                mov     eax,[xE000+0]
                mov     edx,[xE000+4]
                wrmsr
                inc     ecx
                mov     eax,[xE800+0]
                mov     edx,[xE800+4]
                wrmsr
                inc     ecx
                mov     eax,[xF000+0]
                mov     edx,[xF000+4]
                wrmsr
                inc     ecx
                mov     eax,[xF800+0]
                mov     edx,[xF800+4]
                wrmsr
                mov     ecx,0xC0010010
                mov     eax,[xC0010010+0]
                mov     edx,[xC0010010+4]
                wrmsr
                ret

xC000           dd      ?,?
xC800           dd      ?,?
xD000           dd      ?,?
xD800           dd      ?,?
xE000           dd      ?,?
xE800           dd      ?,?
xF000           dd      ?,?
xF800           dd      ?,?
xC0010010       dd      ?,?