Discussion Any suggestions on enhancing pcie extender ribbon cable shielding?


Average Stuffer
Original poster
Jun 4, 2020
I have several of these FPC (Flat Printed Circuit) ribbon cable M.2 M-key extenders, see this as an example of the most recent unit I have tested:
These are great because of their compact size and will always fit well underneath sandwiched GPUs and such extremely tight SFF environments. Typically, I will use these to connect a NIC as a secondary card (e.g. Mellanox ConnectX-3 for 40Gb networking, where these cards would degrade to x4 lanes running an acceptable ~26Gbit/s speed), which is preferable to going down the bifurcation road on the main x16 slot as usually we only really need a single NVMe on the main M.2 slot. (Granted if we wanted full speed an argument for bifurcating main slot for full x8 on such a card is well received)

Actually, even for NVMe's, they will suffer greatly on thermals when left sandwiched underneath a GPU, so even these are worth extending out somewhere else in the case so that they may be cooled.

As a significant side benefit, these FPC ribbons are almost always connected with detachable ends. This is ordinarily not relevant but becomes super useful when trying to make an extreme SFF setup where there's no space in the case for the NIC and a dongle is fashioned to run PCIe external to the case to use in "non-portable" mode. Yeah it is super awkward though because usually these things also require bringing out a SATA power adapter. (But, I did see that it's possible to use some more adapter atrocity to achieve bringing out a single U.2 connector from the case to do this.) When I have no such need for detachability I would always choose a fixed end ADT-Link extender, and those also have many PCIe 4.0 flavors, which is very nice and forward looking and sure to deliver on signaling robustness with regard to PCIe 3.0. As an example, In my X570 ATX workstation (Crosshair VIII Dark Hero) I'm employing one of those PCIe4 extenders right now to run my LSI HBA card off the secondary M.2; there is only one x4 capable slot running off this southbridge, so my other options would be either to limit this HBA to that other x1 slot (ew) or run it on the x8 slot and drop the GPU to x8 (also ew).

Anyway, to cut to the chase, the main drawback with these ribbon cables is that I usually find they tend to drop to PCIe 2.0 signaling when they're routed in close proximity to other components. This of course is an unavoidable situation in an actual SFF where the x16 PCIe riser cable will be in close proximity.

Now, these FPC ribbons generally come with a layer of some foil-style shielding wrapped onto them.

My question is if anyone could tell me what the chances are if I wrap the FPC with several more layers of this or other better shielding and/or insulation if I am likely at all to gain PCIe 3.0 signaling capability back.

If I can't resolve this then these adapters I have here might end up being junk. I was going to be relying on them for my Velka 7 build, as I need the high speed networking to go to this build. I ran fiber to my living room for this purpose. It would be okay to drop to ~12Gbit bandwidth of course, would just be disappointing and I was trying to avoid such a compromise.

Luckily, I:
- found out about the Velka 7's ability to mount the GPU offset in the case higher up, which allows for a great deal of space underneath the GPU with which I will surely be able to nestle at least a single port Mellanox NIC!
- also was able to grab 3080Ti FE for a great deal, which is a perfect pairing for the flow through trick (dual 70mm fans in the 2.5mm tray area in the case, combined with the GPU shift mod). This is going to be a far better GPU cooling situation for this build and brings it much closer to perfection compared to the XC3.

...And so I will be ordering yet another proper fixed-end ADT-Link adapter to set the NIC up to the side of the FE card once it's mounted offset inside!

The question then becomes mostly academic at least for me. But I can see people running into this limitation just like I did. I just happened to have found a way around it because Velka 7 (and the ingenuity of folks on this forum!) is awesome like that. Maybe we would want to look specifically for beefed up shielded FPC compatible ribbon cables if anyone on earth makes them.
Last edited: