Each 7990 consists of 2x S10000 Sever Graphics cards that each total 3G vRam, so if you add them, it totals 12G of vRam.
Other than that, it's a 1200W power supply as the graphics cards alone pull around 1000W, then a dual core intel processer and 4G RAM, and a standard run of the mill HDD.
Here's a vid of the Example stress test, it annihilates it.
Ayylmao, just realized my mic was on