I’m designing a board that will sit in the expansion bay shell and will provide a fully powered (75w max) pcie x16 (only x8 lanes) on the rear of the shell. Are there any features people would like to see on it if i eventually post the geber files?
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Suggestions!
Can you add a ground plane below the pcie traces to improve signal integrity?
Can you add retimers to make riser cables easier?
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Definitely interested and I am just spitballing here, but theoretically, if I had a RTX 3090, and wanted to insert it and power it with another PSU and cables, would it work (mind you, this is not for the average coffee shop)? 
yes it would, that is what i am trying to accomplish here. I have a 4090 in my main rig and a 4070tis but whenever my main rig is unavailable i want to still game but the laptop is too loud with rx7700s and it drain battery bc 180w charger is not powerfull enough
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there are 4 layers
PCIE lanes
GND plane
PCIE lanes
Mainly GND plane + some power and signals
A retimer is a good idea though i only plan to use a short PCIE riser so retiming should not be an issue. ive already impedance matched and trace matched the RX/TX lines. But correct me if im wrong.
I may be wrong but I’m fairly sure the PCIE spec suggests you put the PCIE traces on the top and bottom of the board, with lower speed ground and other signals in-between. Honestly though I’d be surprised if it made any difference, just wanted to let you know.
thanks for the info, that is news, i just finished designing the rigid-flex board and quote is 600$ for 5. Gonna do 2 separate boards and then design and ribbon cable instead.
Great, looking forward! And I know this is pretty early on, but as support I just wanted to say that you hereby have your first customer. I am interested in getting one. 
We have had pretty bad luck with making the connection work via OCuLink 8i, so I am happy to “force it” through this project if possible. It would be more of a desktop setup.
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That’s great to hear! Once I have all the kinks worked out I’ll let you know!
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An 8i board in the works now? Goodness people are really starting to put in some work. Curious to see how this turns out for sure. Do you have any rough draft pictures you can share of what this thing will look like?
sadly not, still in the PCB design phase, im not to familliar with PCIE protocol or what all the extra pins are for so im just praying it works :). if it does then ill do a bunch of optimization and work on it before i publish anything. But here are some photos of some preliminary designs and the github page (which is very outdated) GitHub - Ether-Nova/FW16-pcie-expansion-bay
Well this at least proves you are doing more than just talk about it! It’s certainly a start, and again, I am genuinely curious how this will turn out. Will be following to see the progress.
I have a free weekend so i should be able to do Rev 3 with 2 boards and a flex board
Nice. Out of curiosity, (because I am not versed in boards or lanes etc.) is there a reason it seems like all the lanes are going to one side of where the interposer connects? Or is it because you have lanes running to the other side from the bottom? Does it matter? Sorry for my ignorance, just curious. In addition, do you have an idea of when you might look at making a prototype to test?
in the photo the left side of the interposer is for power and the right contains all the PCIE lanes, you can find documentation here ExpansionBay/PCB Reference Design/FW_EXPANSION_BAY_PCB_0807.pdf at main · FrameworkComputer/ExpansionBay · GitHub
I just ordered this board at the beginning of the week. Its set to arrive sometime early next week so i should be able to start testing next week or the week after that depending on how much time i have
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Very cool. Looking forward to hear results, please keep us posted!