4X Mode or 8x Mode

[nano__]

hi dear , I bought z170a m3 , r9 390x, cpu 6700k i want to go cross fire but when i see on motherboard the pci e4 the slot not 16x(the lanes not the same on 16x ) so if i installing CF what is the mode running 16x/4x or 8x/8x or what and what disadvantage when running 16x/4x vs 8x/8x
the specification on the link http://

 

[13thmonkey]

x16x4 will more constrained by the interface than x8 x8 which is unlikely to be impacted on PCI-E3.0

 

[Rookie_MIB]

According to the manual, from what I can see, it would run in x16/x4 mode. The first GPU in the x16 slot utilizes the 16 PCIe lanes to the CPU, the second GPU in the other x16 slot is wired to the x4 lanes going to the PCH. I'm somewhat surprised that MSI didn't wire this with a switch to allow x8/x8 operation when running dual GPUs. It's an ATX board, they had enough space to run the wiring properly, and with the 'gaming' designation - it would make more sense to make it a full SLI certified board.