NVIDIA Tesla K20C in Dell PowerEdge R720xd — power cables

CptSupermrkt asked:

I am trying to put an NVIDIA Tesla K20C into a Dell PowerEdge R720xd. I’m having a bit of trouble understanding the power requirements of the card.

First, here is a picture of two pages of the same manual, which seems contradictory to me. One page says only a single connector is required, while the next page says both are required. The entire manual for the card can be found here: http://www.nvidia.com/content/PDF/kepler/Tesla-K20-Active-BD-06499-001-v02.pdf

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Here is an photo taken of the power connections on the card:

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And here is a photo of where those connectors need to go, onto the PCI-E riser of the r720xd:

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Neither the R720xd NOR the GPU came with the necessary cables. And given what appears to be a contradiction in the GPU manual (above), I’m not even sure at this point what we actually need. I have searched high and low online for things like 2×6 pin PCI-E to 8 pin male-to-male and so on, and for the life of me cannot find what we need.

In case anyone needs it, the owner’s manual of the R720xd can be found here: ftp://ftp.dell.com/Manuals/all-products/esuprt_ser_stor_net/esuprt_poweredge/poweredge-r720xd_Owner%27s%20Manual_en-us.pdf The relevant page is page 68, which clearly indicates that the 8-pin female port on the riser card is for a GPU.

The bottom line question: exactly what power cables do we need to buy, and where can we find them?

My answer:

To answer your question about the GPU power connectors: Some GPUs only need the power provided by one connector, and will only have one. More high end GPUs will need more power and have two connectors. If two connectors are present, you need to connect both of them, or the GPU will not have enough power to run at its full capacity.

As for the cables themselves, they are easy to find. The 8-pin to 6-pin GPU power cable can be had from a variety of web sites. For the other connector, use a Molex to 6-pin adapter. Note that with these adapters, both Molex connectors need to be connected to power in order to provide sufficient power. Sorting out what to with redundant PSUs is left as an exercise for the reader; it will probably involve Y cables and prayer…

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