Z87M Extreme4: PCIe bandwidth question

Annex wrote: Question about the PCIe bandwidth on the Z87M Extreme. If I already have a 3.0 x16 video card in the first slot, and I put a 3.0 x4 m.2 SSD into the PCIE3 slot, will the video card automatically drop down to x8, providing another x8 to the SSD (and thus wasting x4 worth of bandwidth)? Or would the video card somehow end up with x12?

I'm assuming a Z87M Extreme4 board.

Your first description of the result is mostly correct. The video card will be running at x8, and the M.2 SSD in the (hopefully) PCIe 3.0 x4 adapter card will be running at x4. The M.2 SSD cannot use more than four PCIe lanes, regardless of the adapter card.

Video cards run at either x16, x8, or x4. Ask the video card manufactures about that.

Actually, PCIe slots are electrically connected as either x16, x8, x4, x2, or x1. That's related to the binary nature of computer operation. 12 is simply not used.

The wasted x4 bandwidth would be available in another PCIe 3.0 slot, if your board had one.