PCIe Lanes CPU VS Motherboard

[FAHEYGF87]

I think that I understand a concept, but i'd like to get some validation from you smart people.

 

Here is my hypothetical system:

ASrock X570m Pro4

Ryzen 5 3600

ASUS Hyper M.2 X16 PCIe 4.0 X4 (4x 250gb Samsung 980 pro)(speedy boi data)

ASUS GT 710 X1

1x 250gb Samsung 980 pro(OS)

USB C 10gbps NIC

 

 

According to their respective spec sheets, the X570 motherboard should have "up to 36 PCIe lanes", and the 3600 has 16 PCIe lanes. 

 

I'd like the M.2 card to use the 16 from the CPU, and the video card and the onboard M.2 to come off the chipset. Assuming I put the M.2 card in the top slot, it should run correctly, right? 

 

So with drives/video card/ and M.2 card, i've got 21 lanes used.

 

I'm trying to make sure that the advertised number of lanes isn't a "whichever comes first" sort of situation.

[Kilrah]

Total number or lanes doesn't mean much, what does is what features/slots are on the board and any notice in the mobo manual about some things being disabled when others are used if any.

[Moonzy]

For full x16 speed, connect it to the top x16 slot, that's usually connected to the CPU directly

 

The second x16 slot is usually x4 electrically only, so you can connect your gpu there as it's only functioning as display out I assume and doesn't need lots of bandwidth

 

As for m.2 slot, you can connect it to any slots, if you go through the chipset then that's fine, but AMD CPU have dedicated lanes to m.2 from the CPU too, which is usually the top slot and it won't affect the x16 card

[Kilrah]

Also note that this hyper m.2 card requires the motherboard to support PCIe bifurcation, which is supported by ASUS boards marked as compatible but not every manufactuer enables that on ATX boards.

 

That board seems to support it.