Precision M6600 with Firepro m6100

Hi everyone, this is a message to anybody who has successfully managed to install an AMD Firepro M6100 in a Dell Precision M6600. This is the second time I have tried this installation and in both occasions I get a black screen on startup and I cannot even get into Bios. I have phoned Dell and diven them my service tag <Private data removed from public view. DELL-Admin and they tell me they are not compatible. I wanted to know how you guys managed to do this. Could it be that not all M6600s have the same components in the motherboard hence my M6600 having compatibility issues and others not? Or have I got the wrong setting in my Bios? Thanks for your help