Bios could handle integrated video and separated video card as well.
A remember I see sometime ago on ebay some kind of enabler for onbard graphics card ,was a little pcb.
This is part code
I installed a M3500 video card when i had A10 bios and it worked fine, it was about the same as my 7800go as far as performance...BTW i have a E1705 with T7600 processor and it originally came with a ATI xp1400 and a T5600 processor which were a joke. I'm very happy with my 7800go that Dell accidentally sent as a replacement for my bad ATI xp1400.