I was wondering as well. I have:
A10-5800K proc
AMD radeon 6670 (dual graphics enabled)
patriot viper 3 8GB ddr3-1600 RAM
MSI Fm2-A75MA-E35 mobo
Windows 7
1TB seagate barracuda 7200rpm
And I have, in the bios, set my PC to allocate 2GB of my RAM to my integrated graphics. So essentially I have crossfired 6670s with 2gb VRAM