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I am trying to figure out the following.

The NC552SFP is listed as an eight lane (x8) PCI Express (PCIe) 10 Gigabit network card that can automatically auto-sense between x8 and x4 slots.

If I put it into an x4 slot will I still achieve 10Gb performance on both ports or will performance suffer?

If I can still achieve maximum performance on an x4 slot why is it an x8 card?

Thanks for any explanation.

YAN 写了：I am trying to figure out the following.

The NC552SFP is listed as an eight lane (x8) PCI Express (PCIe) 10 Gigabit network card that can automatically auto-sense between x8 and x4 slots.

If I put it into an x4 slot will I still achieve 10Gb performance on both ports or will performance suffer?

If I can still achieve maximum performance on an x4 slot why is it an x8 card?

Thanks for any explanation.

If you install it into a x4 slot, it will operate as x4 and I think the performance will a little suffer.

PCI-gen2 x4 lane has in theory 2000MB/s in throughput;

if you calculate 20Gb for the dual ported NIC (simplex) then you require 2.5GB/s (in theory).

Then you have consumed already all the performance of a X4 lane on PCI-Gen2;

and then we didn’t talked yet about the duplex traffic.

So yes you will suffer in performance if you put the card on a X4 slot (although it will work);

it might be all depending on the average utilization on both NIC ports if you will see it;

if you use both ports as active/passive (versus active/active) then then might not see the performance degradation.

Of course with PCI-gen3 (Gen8) the PCI-e gen2 speed went up from 5GT/s to 8GT/s so you would not suffer in performance with an X4 card on 10GB but we don’t offer any 10GB device in any way that do support PCI-e gen3;

those PCI-e gen3 cards will only be made for high performing video (NVIDEA) and 20/40Gb IB cards.

I hope this helps?