“The Virtual Windows above consist of eight 15″ LCD panels connected via custom-built cables to two nVidia Quadro NVS 400 PCI video cards, each with four DVI outputs. The LCD backlight inverters are driven by their own power supply (sitting on top of the PC) and the panels get their 3.3v power from the PC’s ATX power supply. The total desktop resolution is 3072×2048.”
More info here.