Dual sfp+ 10gb nic in pciev3 x4

Hessam2013

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Dec 20, 2016
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Hi
My very first post here
I was about to buy my first 10gb nic, during my researches I found out that there is almost no pcie gen3 dual sfp+ 10gb nic with x4 edge connector, as the bandwith provided by x4 gen 3 is enough for 40gbps full duplex, is there any reason(backward compatibility, etc) why cards are still built with x8 edge connectors?
Does using these card in x4 electrical slot give the expected performance?

Regards,
Hessam
 
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Patrick

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Dec 21, 2010
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One other important aspect is whether the 10Gb SFP+ NIC is PCIe 3.0. Many are PCIe 2.0 so you do not get PCIe 3.0 bandwidth from them.
 

Hessam2013

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Dec 20, 2016
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One other important aspect is whether the 10Gb SFP+ NIC is PCIe 3.0. Many are PCIe 2.0 so you do not get PCIe 3.0 bandwidth from them.
Tnx Patrick,
I will edit my question, I already meant those cards that are gen 3 capable

Regards,
Hessam
 

Hessam2013

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Dec 20, 2016
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Don't forget the pcie overhead: there are layers like in the osi or tcp/ip stack for pcie. You will need at least 40 gbit + bandwidth for the pcie headers, checksums and so on.

Down to the TLP: How PCI express devices talk (Part I) | xillybus.com

I386, Tnx for respons and link
As my calculation says, gen3 is nearly 8gbps per lane per direction, and thats 32 gbps in x4 link in one direction or 64 gbps full duplex, isnt it enough room for 40gbps that a dual sfp+ card needs?

Regards,
Hessam
 

PigLover

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Jan 26, 2011
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Also don't forget that many manufacturers use a common board design for multiple products. Mellanox, for example, uses the same chipset and same basic board design for their 10Gbe, 40gbe and 40/56GB Infiniband products - then they just mount the right rev of the chipset and the right connectors to "personalize" it into a 10Gbe "EN" card or a multi-protocol 40/56GB "VPI" card.

Using PCIe 3.1 at the card edge for all of them actually saves them a lot of money. And the segment of the market that might want an x4 card just isn't big enough to get them to react.
 
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