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Comment by buildbot | Hacker News Reader

The SXM2 interface is actually publicly documented! There is an open compute spec for a 8-way baseboard. You can find the pinouts there.

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I had read their documents such as the spec for the Big Basin JBOG, where everything is documented except the actual pinouts on the base board. Everything leading up to it and from it is there but the actual MegArray pinout connection to a single P100/V100 I never found.

But maybe there was more I missed. I'll take another look.

Upon further review... I think any actual base board schematics / pinouts touching the Nvidia hardware directly is indeed kept behind some sort of NDA or OEM license agreement and is specifically kept out of any of those documents for the Open Compute project JBOG rigs.

I think this is literally the impetus for their OAM spec which makes the pinout open and shareable. Up until that, they had to keep the actual designs of the baseboards out of the public due to that part being still controlled Nvidia IP.

Hmm interesting, I was linked to an OCP dropbox with a version that did have the connector pinouts. Maybe something someone shouldn’t have posted then…

It would be a shame if such a thing were to fall off the back of a truck as they say

I could find OCP accelerator spec but it looks like an open source reimplementation, not actual SXM2. That said, the photos of SXM2-PCIe adapters I could find look almost entirely passive, so I don't think all hopes are lost either.

couldn't someone just buy one of those chinese sxm2 to pcie adapter boards and test continuity to get the pinouts? I have one that could take like 10 minutes

I have one, my plan was to map the pin out. My six month old has different plans for me which involve me not sleeping.

If you're willing to do the testing and post the pin out, I'll send it your way.

Would like to have it sent back when you're finished though, and I'd pay shipping both ways.

I do have the ground pins mapped out and could share that which should save some time.

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