I hacked external PCIe connectivity on the Atomic Pi!

[ginbot86]

Man, this was one of those projects where one thinks "Oh, this'll be easy, just gotta wire it all up"... but everything goes wrong. It took a lot of work and many different attempts, but I was able to break out the PCIe bus from the Atomic Pi, which was originally used by the onboard RTL8111G Ethernet chip. The issue was a lack of any accessible points to add an external connector, but I eventually found a working method.

My blog post is here: https://ripitapart.wordpress.com/2019/06/25/atomic-pi-adventures-episode-1-adding-external-pci-express-expansion-by-removing-onboard-ethernet/

[magic]

Sounds fun

It may have been stubs and parasitics of the Realtek chip which frustrated your early attempts. At 5gb/s one bit is 4cm long so 1cm stub to the chip and back adds a signal delayed by half bit