Introducing the Hat uPCIty Lite - our PCI Express evaluation board with an open ended PCIe X4 slot. Compatible with Raspberry Pi 5.

Key Features and Strengths:

Specially Designed for Raspberry Pi 5: Tailored for the latest single-board computer, the Raspberry Pi 5, ensuring perfect compatibility.
Test new hardware just like we do: The uPCIty line used to be our secret weapon and now we open it to all the makers.
Open ended PCIe X4 slot: Yes, you can connect your RTX 4090 to the Pi. We won't stop you.
Support for external power: The board can supply 12@8A to your card from a standard ATX power connector. You can also use a barrel jack for less power-hungry applications.
It won't fry your Pi: We wanted to play it safe and decided to isolate the PCIe Express power delivery from your Pi. This approach also reduces the heat output from the board and it is very important considering the small footprint. We recommend the official 5V@5A power supply for your little computer.
PCIe Interface Support: Compatible with PCIe x1 interface in both Gen2 and Gen3 standards, offering versatile connectivity.
Compatible Form Factor: Maintains compatibility with original Raspberry Pi HAT dimensions of 65 x 56.50 mm, ensuring a cohesive fit.
High-Quality Components: Built with premium electronic components and a 4-layer PCB for reliability and performance.
All Necessary Accessories Included: Includes a dedicated FPC PCIe ribbon, spacer pins and M2.5 screws ensuring a complete setup out of the box.

Documentation and tutorials are available here: https://pineboards.io/pages/documentation