Some 790GX boards are coming with integrated graphics chips, the 3470, officially known as 3300 to put the part number against the performance, obviously. Some of these boards, like one from Gigabyte for example the GA-MA790GP-DS4H has 128MB of GDDR3 sideport memory. Now, I know it's possible to combine the performance of this integrated chip with, say, a 3870 graphics chip, but does this extend to the 4xxx chips as well? For example, could a 4870X2 chip go in, and combine the power of the integrated chip with that discrete chip? Poor example, I know, because the 4870X2 is leaps and bounds over the 3470 in terms of performance...

I'm afraid I have no idea if that would work. Is the 3 series compatible with the 4 series?

The last I heard was that these were not compatible.
The last I heard was also not clear as to whether this included the mix of IGP's with actual cards.