ROG B350-F PCI-E lanes and M2 NVME

[boosted1g]

Looking for a Ryzen guru that knows how the PCI-E lanes are distributed.

Background:
I am looking at doing a ryzen 1700 build with ROG B350-F board and trying to decide whether to get a 960 evo or 850 evo M2. I know that many say you don't see much speed difference but at $27 difference on Amazon might as well.
Not that it makes a difference but I also plan on upgrading from my 750 ti to a 1060 for this build.

If I understand correctly on the Ryzen PCI-3.0 bus I can have x8 for GPU at the primary x16 slot, x4 at secondary x16 slot available to me, x4 for NVME; and then still have all x4 lanes of the board's PCI-E 2.0 bus. Is that correct?

If not, then by getting an 850 evo and having it pull the bandwidth from SATA instead of PCI-E will I then still have x4 open PCI 3.0 lanes and x4 PCI 2.0 lanes avaliable for expansion (using x8 for GPU)?

 

[TJ Hooker]

If I understand correctly on the Ryzen PCI-3.0 bus I can have x8 for GPU at the primary x16 slot, x4 at secondary x16 slot available to me, x4 for NVME; and then still have all x4 lanes of the board's PCI-E 2.0 bus. Is that correct?

According to Asus' specs, yes that would seem to be right. However, according to AMD's own specs for their chipsets, the only chipset that supports splitting CPU PCIe lanes is X370, so B350 would only support a single x16 PCIe link to the CPU. I'm kinda confused...

 

[boosted1g]

Yeah I could not seem to get a completely straight answer from my research.

Ryzen has 24 lanes, but at least that b350 board only seems to have 20 available (x4 for single M2 slot and x16 for GPU)

I assume by putting a card in the second PCI-E slot autoswitches to x8/x4 then?

On a side note, anyone know of a M key to USB adapter. Want a way to clone/restore/transfer in case I have to directly interface with my home server which does not have M2 (and I have nothing but x1 slots free on it)

 

[TJ Hooker]

Ryzen has 24 lanes, but at least that b350 board only seems to have 20 available (x4 for single M2 slot and x16 for GPU)

I assume by putting a card in the second PCI-E slot autoswitches to x8/x4 then?

All Ryzen CPUs dedicate 4 PCIe lanes to their connection to the chipset. And then the other 20 are allocated like you said (not sure if 4 lanes are always dedicated to M.2, or if a mobo manufacturer could potentially free those 4 up for general use).

But like I said, according to AMD only X370 allows splitting the x16 CPU link into x8/x8 (same as Intel and their Z series mobos). http://www.amd.com/en-us/products/chipsets/am4
That's why I don't understand how that B350 mobo can have PCIe 3.0 x8/x4 + PCIe x4 for M.2 all active at once...