The machine in the clip is running an AMD Fusion - probably a low-power A10-4655M chip (owing to the total paucity of this model on the market, which would make sense if it was earmarked for tech demo builds) - on a custom-fabbed miniITX board. Said chip has an on-die integrated video card (reasonably good, though by no means high-end) so no need for a dedicated one (unless you want m0ar dakka via Hybrid Crossfire, though I don't think you'll be able to fit one, given the tiny headroom). What I find odd, however, is that Valve are going the AMD Fusion route, since Sony (their would-be rivals in the console market) have recently been showcasing several demonstators of their own, running the same Fusion APU (Accelerated Processing Unit). Then again, Sony have the glut to bide their time, so they might be waiting for AMD's 28nm Kaveri APU, rather than going for the current Trinity. Edit: Lemme guess, a good deal of the stuff I've written is Sanskrit to many AdvRiders.