What exactly did I buy? (Mellanox PCIe card)

doop

Member
Jan 16, 2015
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Dear forum

Let me preface this by saying that I've never done any networking other than connecting my computer to the wall to get Internet. So I was reading about this supercool 10Gbe network stuff and decided to check out how much it was on eBay. I stumbled over an "Ethernet Adapter PCI-E MCX312A-XCBT" ( Ethernet Adapter PCI E MCX312A XCBT | eBay ) for $50. This seemed really cheap to the other ConnectX 3 stuff, making me instinctively buy it o_O

Realizing I have no need for such a thing, I started googling to find out what I had bought this time...
The eBay description says it's a "Mellanox ConnectX-3 FDR VPI IB/E Adapter" and when I googled the MPN I found the same on http://www-01.ibm.com/common/ssi/rep_ca/8/897/ENUS113-008/ENUS113-008.PDF . IBM also says it has QSFP connectors(!). This is a bit confusing since mellanox.com says MCX312A-XCBT (from the title) is a 2port 10GbE SFP+ card (no Infiniband, only Ethernet).
When comparing the picture from eBay to other cards, the connectors also looks more like what's found on QSFP cards.

Is this indeed QSFP?
Can it do ethernet at all? I'm hoping /E means ethernet!
How does one connect stuff to QSFP? With SFP+ it seemed like I only needed to buy some kind of transceiver. With QSFP I'm finding lots of expensive stuff that appears to convert it into 4xSFP+. Does this mean I get 2x4x10Gbe? :p
 

PigLover

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Jan 26, 2011
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The part number is for an 'EN' card - dual SFP+ 10gbe, no infiniband.

The photo and description are of an FDR VPI card - 56gbps infiniband or 40Gbe ethernet.

One of these is wrong. The part number does not match the picture/description.

Either way you got a decent deal. If it is the EN card it should resell for $90-125. If it is the VPI card $175-250.
 
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doop

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Jan 16, 2015
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Thank you, sir! It will be like a second christmas then - not knowing what's in the package!
 

Chuckleb

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Mar 5, 2013
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You can get a $30 QSFP+ -> SFP+ adapter allowing you to use the 10GbE DAC cables or fiber cable. They work great. We have 50 or so in our servers.