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Deadbugging PCIE 3.0 GPU 8GHz

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invalid_syntax:
First time poster, if wrong board, please recommend (RF ?)

I am trying to see the possibility of deadbug style connection to this GPU.

https://i.ebayimg.com/images/g/p3IAAOSwz2plQqT9/s-l1600.png

- Pins are 1.67mm aparts. Soldering doable (* would help is thin wire can be used)
- Total of 32 Differential Pairs ( Or 16 if gpu supports x8 downgrade).
- Connecting to a PCIE Male connector going to motherboard.
- Using 3M Twinax for the cable - https://www.digikey.com/en/products/detail/3m/SL8802-08-20DN5-00/3837412
- Wanted to test it before/while working on the PCB with proper socket.

While i wait for the gpu to arrive or begin testing. I have following two major concerns.

1. Instead of connecting the twinax directly to the pins, is it possible to use a twisted pair, or twisted pair + several gnds thin wire like magnet wire 1-2 CM to a landing pad with many pins from where the Twinax will continue.

2. The twinax does not have a drain wire per differential pair. It has two GND wires at opposite ends of 4 diff pairs. Waiting for the cable to arrive as well. If the shield is not grounded, do i need to ground it or not necessary for diff pair as long as return line is present ?

Edit for additional details.
- Data sheet for cable: https://multimedia.3m.com/mws/media/673519O/3mtm-twin-axial-cable-sl8800-series.pdf
- GPU is SXM2 P100

inse:
I have no specific knowledge about PCIe but I expect signal skew to be absolutely relevant here.
The proposed cable has solid conductors, they would break off already during soldering.
Good luck on that…

ajb:
Seems like it would be a LOT less work to design a simple adapter PCB, on top of being more useful.  There's a lot that can go wrong here, not just with signal connections but you also need to somehow get 300W into the thing.  Hard enough to get all of that right on a PCB, let alone hand soldering flying leads onto a 1.6mm pitch grid.

Do you have experience designing things like this? 

tooki:

--- Quote from: invalid_syntax on March 13, 2024, 03:50:16 am ---First time poster, if wrong board, please recommend (RF ?)

I am trying to see the possibility of deadbug style connection to this GPU.

https://i.ebayimg.com/images/g/p3IAAOSwz2plQqT9/s-l1600.png

- Pins are 1.67mm aparts. Soldering doable (* would help is thin wire can be used)
- Total of 32 Differential Pairs ( Or 16 if gpu supports x8 downgrade).
- Connecting to a PCIE Male connector going to motherboard.
- Using 3M Twinax for the cable - https://www.digikey.com/en/products/detail/3m/SL8802-08-20DN5-00/3837412
- Wanted to test it before/while working on the PCB with proper socket.

While i wait for the gpu to arrive or begin testing. I have following two major concerns.

1. Instead of connecting the twinax directly to the pins, is it possible to use a twisted pair, or twisted pair + several gnds thin wire like magnet wire 1-2 CM to a landing pad with many pins from where the Twinax will continue.

2. The twinax does not have a drain wire per differential pair. It has two GND wires at opposite ends of 4 diff pairs. Waiting for the cable to arrive as well. If the shield is not grounded, do i need to ground it or not necessary for diff pair as long as return line is present ?

Edit for additional details.
- Data sheet for cable: https://multimedia.3m.com/mws/media/673519O/3mtm-twin-axial-cable-sl8800-series.pdf
- GPU is SXM2 P100

--- End quote ---
This seems like a fool’s errand to me that will just result in a dead GPU and a bunch of wasted cable and time.

Either design your PCB now, or contact this dude who is willing to share his design files for the same thing: https://www.reddit.com/r/nvidia/comments/l7gon4/is_it_possible_to_convert_from_the_sxm2_interface/

nctnico:
I'd design a test PCB for sure. Using wires is going to end up nowhere; PCIe (and similar high speed signals) really need tight impedance control.

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