I have been trying for quite some time to get a "HP AMD Radeon HD 6450 512MB PCIEX16" GPU to work. I have a HP 6200 Compaq pro SFF, so my gpu options were limited but I picked what I thought was the best of them. After installing the GPU, my PC would turn on but the screen stays black (so that kinda eliminates the option of Ubuntu installing the driver as far as I know). I'm guessing that's because it is trying to use the GPU I just installed instead of the imbedded graphics. I took the GPU out and scoured the BIOS and found no option to change anything GPU related in there (and it looks like others have had the same problem and just updated the BIOS, but on Windows). I checked the HP update list on Ubuntu's website, but my PC was not listed so I cannot update the BIOS that way either. I browsed through AMD's website, and I couldn't find anything for my particular GPU (although I'm new to linux in general so I could have looked at it and had no idea I was). I really don't feel like downloading Windows again at 200 kb/s just to update the BIOS then install Ubuntu again. Any ideas on how I can get this thing working?
Try going to the Unity search by clicking the top left icon in the Unity launcher. From there search "system settings" and you should find a program bearing the same name as the search. Click that and you should see an icon called "Software and Updates"; click there. Go to the last tab called "Additional drivers" and download whatever drivers you may deem necessary. I had to do the same thing with my old Geforce 6300. Hope it works!