So today i got some good info toward the use of the PCIe 1 to 3 hubs available online...
So over in the miner rig porn pages, there is a fellow who builds a lot of 1 mobo to 8-12 GPU rigs and i just didnt understand how he was managing all of this so i messaged him and this is what he mentioned to me..
It really all comes down to the CPUs that you are using.... for example the Intel's LGA-1156, LGA-1155, and LGA-1150 sockets have a single 16x PCIe port on the CPU. This port can be broken into three subports in the following configurations: 16/0/0, 8/8/0, 8/4/4. Each subport can be down negotiated independently, so it's possible to use configurations such as 4/4/4, 4/1/4, and 8/0/1. It is not however possible to connect more than three PCIe devices to this port without using an external switching chip.
Intel's Platform controller hub has an additional 8x PCIe 2.0 port which can be broken down into 8 individual 1x ports which enables the use of numerous low-bandwidth peripherals and add-in chips. Most motherboards contain a 4x port and up to three 1x ports. These ports often share bandwidth (on motherboards that contain an M.2 connector, this shares bandwidth as well) which means that the 4x port can operate in either 4x mode or 1x mode. If none of the 1x ports are populated, it will operate in 4x mode, if any of the 1x ports are populated it will operate in 1x mode for a total of four 1x connections to the PCH.
So to run 8 GPU's you have to purchase a CPU that supports atleast 8 independent ports, not all CPU's that state having 16 PCIe channels work well with multiple independent configuration, mainly server and more expensive CPU's are the ones that are coded to properly work well with 8 independent channels communicating at one time..
So example... Intel i3 6100, its rated at 16 PCIe channels MAX, 1x16, 2x8, 1x8+2x4
So in theory the x16 slot can be broken into 3 independent channels, then all other ports used in 1x, but many motherboards share the bandwidth between the x8 slot and the x16 slot to save money, so you have to figure out what configuration the motherboard is wired firstly to correctly adjust the settings in the bios for it to run. The motherboards that dont share bandwidth allow you to run 3 x GPU's off the x16 slot in (4/4/4), then 2 additional off the x8 slot in (1/1), then utilize the rest x1 slots as singles.
Most fail to use them correctly, because they try to use CPU's with basic PCH control, which doesnt support anything more than 1 independent channel per port to communicate.
The other reason they fail to use them is the fact they have to view the video on the computer to see what they are doing, so they hook a monitor up to the computer, which depending on your GPU auto changes the port priority. Most AMD cards require minimal x4 to work correctly, while most modern Nvidia cards require x8 to work correctly. So they hook 8 GPU's to the computer, go to boot it up and the PCH auto mandates lets say x8 to the viewing GPU on bootup, what this does on the main x16 slot is forces it into (8/0/1) mode, so the video will show up but not all GPU's will show up on the system or the mobo will fail to boot because your demanding to many channels on a mode that has a null (0) channel. you have to setup the bios from remote access to properly setup 8+ GPU's on modern mobo's
this sounds very likely to be true.