Why do I have two drives on bus 0?

I have an X99 motherboard where the chip set provides for 10 SATA ports. I attached an SSD to port 1 and six hard drives to ports 2 to 7. Now, I know that Windows doesn't refer to ports but to buses instead. I expected that Windows reports the SSD on bus 0 and the hard drives on bus 1 to 6. However, I get the SSD (port 1) as "disk 1" on "bus 0", and one HDD (port 2) as "disk 0" but also on "bus 0". The following five hard drives are "disk" 2 to 6, resp. on bus1 to 5. Can someone explain that to me? Why do I have two drives on one bus? Are they sharing the bus, and why?

Moved to appropriate area...

Windows 10 How-To Guides is for write ups of prepackaged solutions... Not for leading questions on issues not yet resolved.

Hmm .. now where did it land? Where is this "appropriate area"?

Bump .. no one out there to answer my question? Any suggestions where to go or what to look up? I'd really appreciate any help with this.