Are 100G Omni-Path DAC compatible with Ethernet NICs?

[ako9e]

So,

I've goofed up a bit and bought Intel Hitachi IQSFP26C30 QSFP28 100Gbps DAC which appears to be Intel Omni-Path, not Ethernet

(Google search-ing the part number doesn't give much, but the cable has a custom sticker that says "Omnipath")

I'm wondering if I could use it with Ethernet NICs (e.g., ConnectX-6) as a regular DAC?


Before potentially frying a $200 NIC to find that out, I'm trying to find some evidence first...

Both 100G Ethernet and Omni-Path connectors are QSFP28, both adhere to SFF-8436, so the probability of frying is low(-er). The pinouts of both match exactly (I compared the relevant Amphenol cables' datasheets). However both have pins for SCL, SDA, Reset, ModSelect, etc. – so I'm wondering if DACs have some sort of microcontroller inside for protocol negotiations or identification, or whatever, that can impede my intended use of the cable?

 

[i386]

No, Omniparth is a proprietary protocol (based on qlogics infiniband ip)

Edit: I should read the complete posts before writing my answer
A dac cable should work with all supported protocolls. It's possible that a switch accepts only verified (coded) cables...

 

[ako9e]

Now I know the protocol itself is not compatible with Ethernet, but cable is passive and, in theory, should be a protocol-agnostic SFF-8436 since Amphenol datasheets look really identical except the title.

 

[ako9e]

A dac cable should work with all supported protocolls

But that's the thing, it's not supported, not officially, and nowhere I could find.

I used Amphenol products for a reference, and they have a page for generic 100G QSFP Cable Assemblies, which mention Ethernet, Infiniband, SAS, etc. but not Omni-Path. And they also have a separate page for Omni-Path Copper Cable Assemblies 100G. But both look absolutely identical. (Maybe it's just for some specific Omni-path certification?) I asked Amphenol support but they know nothing either.

EDIT: dang, I just noticed that generic 100G assemblies mention EEPROM! So that's certainly won't match that of Omni-Path DAC The only hope that it's not being used/checked. Or maybe I could override it with that of a real Eth 100G DAC? Or is EEPROM only for validating authenticity? But ConnectX aren't DAC-picky AFAIK.

 

[nexox]

However both have pins for SCL, SDA, Reset, ModSelect, etc. – so I'm wondering if DACs have some sort of microcontroller inside for protocol negotiations or identification, or whatever, that can impede my intended use of the cable?

They have a basic EEPROM to provide information to the connected system, this may or may not really matter, DACs generally don't have vendor locks enforced, and they will often run protocols that aren't advertised in the data blob - I've been using a DAC for 10GbE that only advertises 8Gb Fibre channel and 1GbE, no issues. I think you will probably get away with this, unless some of your hardware is very picky.

 

[klui]

Just 1 data point. I tried an Intel OmniPath AOC and it did not work on my Mellanox/Celestica switches, nor Mellanox CX3 NICs at that time. Perhaps it's an AOC and sometimes they more susceptible to incompatibility problems.