x470 PCIe Configuration Question

[sphbecker]

I want to re-purpose an x470 board as a home server (Asus PRIME X470-PRO). Considering a server doesn't need high bandwidth GPU, this is what I plan to do.

 

--Plug GPU in one of the bottom (chipset connected) slots so the system will POST

--Plug 8 lane server multi 10gig NIC into top PCIe slot

--Set board in 2x8 SLI configuration instead of 1x16 so that PCIe slot 2 can also be used by a high-bandwidth card if needed

 

Does anyone know if that will work, or do the top slots only work with a GPU?

[mariushm]

You shouldn't need to set up SLI configuration, slots should automatically switch to 2 x8 slots when you insert a 2nd card.

You should be able to install a video card in 1st slot and the 10g card in 2nd slot and both should get pci-e x8 from cpu, unless the bios has some quirks and insists on both devices be video cards.

 

You can install the network card in the bottom pci-e x16 slot.

The bottom is pci-e 2.0 x4 electrically which means maximum 2 GB/s (4 lanes x 500 MB/s per lane) of bandwidth... after overhead and other things, that's about 1.9 GB/s of actual data transfer between slot and chipset.

 

Keep in mind that 10g transfer is approx. 1.25 GB/s, so a dual port 10g ethernet card will work just fine in such slot, because it will probably rare the situations when BOTH ports are running at full 10 gbps. 

If a a single port is heavily used, it will be able to do full 10 gbps. If both ports on such a 10g card are used, I would guess speeds of  around 700-800 MB/s on each port should be achievable.

 

 

 

[sphbecker]

1 hour ago, mariushm said:

You shouldn't need to set up SLI configuration, slots should automatically switch to 2 x8 slots when you insert a 2nd card.

You should be able to install a video card in 1st slot and the 10g card in 2nd slot and both should get pci-e x8 from cpu, unless the bios has some quirks and insists on both devices be video cards.

 

You can install the network card in the bottom pci-e x16 slot.

The bottom is pci-e 2.0 x4 electrically which means maximum 2 GB/s (4 lanes x 500 MB/s per lane) of bandwidth... after overhead and other things, that's about 1.9 GB/s of actual data transfer between slot and chipset.

 

Keep in mind that 10g transfer is approx. 1.25 GB/s, so a dual port 10g ethernet card will work just fine in such slot, because it will probably rare the situations when BOTH ports are running at full 10 gbps. 

If a a single port is heavily used, it will be able to do full 10 gbps. If both ports on such a 10g card are used, I would guess speeds of  around 700-800 MB/s on each port should be achievable.

 

 

 

Thanks, for some reason I was thinking that if you didn't manually set the SLI option in BIOS that slot 2 would route to the chipset instead, but now that I think about it, that would require a lot of complexity to design and has no real use-case.

 

Thanks for your suggestion, it is unlikely I will have two high-bandwidth cards, so I can probably keep the GPU in slot 1. I am curious if it would function in the chipset connection 4 lane PCIe 2.0 slot. For a server there is literally no need for the GPU...I would just connect a USB attached GPU if I could, but I know the system would fail POST, lol