[VladRussian]

>I'd like more information on the CPUs and CPU/GPU bus of this FASTRA II.

"the graphics cards, which are connected to the motherboard by flexible riser cables." - so this sounds like typical PCIe based design. Usually the bundle of GPU cards on PCIe backplane is placed into separate case which connected back to the CPU host, and in this case they engineered it into one big case thus each card getting it's own x16/x8 pipe.

In general such "supercomputer" is cheaper, hardware-wise, than equivalent CPU-based, yet it is still more expensive human labor (ie. programming) -wise.