Dell Optiplex 7010 SFF: Make integrated graphics always enabled

[iMSannob]

Hi All,

The bios of Dell Optiplex 7010 SFF always disables my i7-3770T's HD4000 when there is no monitor connected to the onboard Displayports.
My bios' Primary Display tab only has three options:
1. Auto
2. Intel HD 4000
3. AMD Radeon WX4100

When selecting "3. AMD Radeon WX4100", HD 4000 will be disabled automatically even though the bios description says integrated graphics will be enabled when Auto is not selected.

When selecting "2. Intel HD 4000", my monitor doesn't display anything during POST.  I can't rollback my bios settings without a CMOS reset.

When selecting "1. Auto", I have to connect my monitor to the onboard Displayport and wait for the operation system to boot after a black-screen
POST. And then I can reconnect the monitor to WX4100's Displayport.

Not like some other motherboard's bios, this bios doesn't have "always enabled" options for integrated graphics device.

Could anyone let me know how to locate the assembly codes that enables/disables HD4000 graphics device inside the bios file?
I would need this information as a starting point to hack the bios.

Thank you.

-iMSannob