POST/BIOS on secondary display ?

I've recently bought a Optiplex 5490 AIO, from a carboot sale "as spares or repairs" (the display was in a very bad condition and since the seller was only asking for a £10 id decided to get it either for parts or to try and repurpose it as either a little media centre or a homelab environment. Got home, connected a monitor on the DP ,plugged it in and surprise Windows booted. So far so good, since everything apart the display seem to work, got my flash drive to install linux on it. but surprise again :( there is no output on the second monitor whilst booting or bios. I have tried all the Fn+Fx or all the Fs but no luck on changing outputs. I've then open it up and completely removed the broken screen including the LVSDS and backlight cables thinking if it wont see any display it will automatically switch to external but no luck with that wither :(. 

Is there any way to force video output on the secondary display ?

I need to go in bios and change settings and also boot from a flash drive to install a OS. So far it's only blank and external display only shows something when windows is fully loaded and asks for login.