About the performance in the homepage of oclHashcat

I notice that, in the homepage of oclHashcat, there is the performance of some kind of GPUs. One of them is

"PC4: Ubuntu 14.04, 64 bit     Catalyst 14.9      8x AMD R9 290X     stock core clock     oclHashcat v1.35"

PC4 used 8x AMD R9 290X GPUs to crack passwords. Does one mother board support 8 GPUs? What is the model of the main board?
Or it uses "VirtualCL"? But as wiki says, "VCL is no longer recommended for oclHashcat clustering, and most likely will not work if you attempt to do it anyway".

I'm wondering how to realize 8 GPUs cracking passwords at the same time.