with intel one slot runs off the cpu at 16x 2ed runs off cpu and shared with the chipset to achieve 8x8 to make NVidia sli requirmens . with a z97 you have to look at how the slots are ''wired''
haswell 16 pcie lanes 16/0/0, 8/8/0, and 8/4/4
now like with z170 - PCIe layout needs a bit of explaining. The top full length slot is x16, which is then followed by a PCIe 3.0 x4 from the chipset. Then we get a PCIe 3.0 x8 from the CPU, and then a PCIe 3.0 x4 from the CPU as well. This technically gives an x8/x4/x4 arrangement from the processor, but with that chipset based slot in the middle between the main x8/x8, we can get a two-card SLI configuration plus another full length single slot device between them without breaking SLI
so if not carful on how they got things worked out on this with the board you can add a 3ed card and loose that 8x on the 2ed card slot for sli
as with this board
The three PCI Express 3.0 x16 slots are controlled by the CPU, with the first slot working at x16 when only one video card is installed, the first two working at x8 when two video cards are installed, and the first working at x8 and the other two working at x4 when three video cards are installed.
so when using multi cards in any slots you got to look at all this so you don't get short changed
with intel the cpu has 16 lanes to work with and the chipset has like 20 ?? so it like a rob peter to pay paul ..
amd runs all off the chipset and don't have this limitation all pcie if run through the chipset until all chipset lanes are used up [I think up to 40 [??] '' chipset provides a total of 38 PCIe 2.0 lanes and 4 PCIe 2.0 for A-Link Express III solely in the Northbridge''