Just received the Pimoroni Bottom adapter from across the pond today. Oddly, the ribbon cable is actually longer than the the one used with the top adapter I'm using, Not by much and because of its S shape as the connectors on the Pi and Adapter aren't aligned. I'm not sure the length of the traces matters much since the top adapter carries those signals from the connector clear to the other end of the board (see pic above).I am not sure if you would get a shorter cable with a HAT, if you want to keep the Active Cooler, if the connector on the HAT is on the "top" side. After playing with a couple HATs I think you will need a riser/extender on the header to clear the cooler. The Pimoroni Base is definitely closer to the Pi PCB than my DigiAMP+ HAT ended up, in terms of the vertical dimension.In addition to how accurately the differential pairs are laid out on the board I think the error rates are also related to the length and quality of the cable. I'd guess hats are better than the bottoms because of a shorter cable, but maybe other factors are more important.BTW. That's half of what I get from a PCIe v3 x4 interface. Not bad at all.
I have also seen a NVMe HAT where the connector was located more towards the middle and fed down through a slot in the HAT to the PCIe connector on the Pi.
Statistics: Posted by lurk101 — Tue Jan 30, 2024 1:06 am