PCI-E lanes for new build on X470/x570?

[bobo89]

Hey All,

 

I'm trying to architect a new unraid build and the pcielanes have my head spinning. I am going for a "do it all" build, which focus on having snappy desktop performance out of a linux and windows virtual host, with performance of everything else secondary. There will be 3-4 vms, and 3-4 docker containers.

 

The proecssor will be a Ryzen 9 3900x or 3800x, undecided.

 

This sytem will have to have:

2x  Rx 480s, 1 for each virtual hosts, so these can run at 8x, so 16 lanes

2x  m.2 NVME drives, each taking 4x. 8x lanes

1x Pcie to 4x1Gb network (something like this Pcie to GB) I don't know how many PCIe lanes this needs, but I'll assume 1.

8x sata drives hooked up

 

So I count at minimum 25 PCIelanes, not accounting for the sata drives and that would leave me with no expansion.

 

So the questoin is how many pcie lanes does x470 and x570 have with the mentioned processor? Can I save some money and go with x470?

The literature available on this topic is not straight forward. Thanks!

 

[testdasi]

In that case you need X570. Based on spec, the X470 can't handle 2 4x NVMe.

[bobo89]

I think I should have been clearer, but a throughput of 2 GB/s is good enough for me on M2, nvme. This x470 board has 2 M2 slots, one at PCIe3x4, and the other at PCIe2x4, which is good enough in speed (https://www.msi.com/Motherboard/support/X470-GAMING-PRO-CARBON#down-manual)

 

But question sitll stands, on how many PCIelanes does each chipset have, and is x470 enough.

[testdasi]

52 minutes ago, bobo89 said:

I think I should have been clearer, but a throughput of 2 GB/s is good enough for me on M2, nvme. This x470 board has 2 M2 slots, one at PCIe3x4, and the other at PCIe2x4, which is good enough in speed (https://www.msi.com/Motherboard/support/X470-GAMING-PRO-CARBON#down-manual)

 

But question sitll stands, on how many PCIelanes does each chipset have, and is x470 enough.

You seem to be pushing hard to justify the X470, in which case, why ask questions?

 

To use the 2nd M.2 slot, the bottom PCIe slot will be disabled. So you are back to the same problem i.e. have no expansion. So is the X470 "enough"? It's certainly not with your requirement to have further future expansion.

 

Also, usually the 2nd M.2 slot is connected to the chipset with means it can't be separated from the other devices without ACS Override - which may or may not cause problems. So even the X570 may not allow you to pass through both NVMe's to VM's. There's no way to ascertain the exact layout and IOMMU grouping without owning the actual board.

[bobo89]

I was only looking x470 to save some money, but after reading some of your design builds, and this is going to be a long term build, I have gone with threadripper.

Thakns for the feedback!