The reason you see one fan in the BIOS is due to the fact that you can't have all eight fans report to one header. The hub works by having signal come from one out X number of fans(being the CPU fan or the main fan that you want the signal to correspond to) so that the header sees one fan, sends the appropriate voltage to the hub and that is passed down to the other fans.
If it's a PWM hub you should have all fans that are connected on to it also be PWM fans.
P.S: same thread topic, merged. Don't create multiple threads on the same topic.