User showcases custom OCuLink X8 module for the Framework Laptop 16 with 1-2% performance hit

Even though Thunderbolt 5 was introduced last year as a superior connector in theory, OCuLink remains the preferred connection for external GPUs. OCuLink, particularly the x8 (full bandwidth) variant, achieves better performance because it is a direct PCIe extension with less overhead, whereas Thunderbolt 5 uses controllers at both ends, which adds overhead and reduces its effective speed when facilitating connections for external GPUs. However, OCuLink, just like Thunderbolt 5, is not yet a mainstream connector on current laptops. Only a handful of laptop OEMs feature OCuLink in select models and the implementation usually integrates the x4 variant instead of the full bandwidth version. One of the first laptops to benefit from an X8 OCuLink connector is the Framework Laptop 16, and, interestingly enough, this implementation is a community-based solution rather than one offered by Framework itself.

Framework expressed some interest in offering an OCuLink expansion bay module a few years ago, but an official solution has yet to be presented. The members of the modular laptop community decided to take matters in their own hands and one of the Framework forum users named Filip recently showcased an OCuLink expansion bay module that makes full use of all eight PCIe lanes.

Filip states that his module is based on Framework’s public repository, but he needed to make some modifications in order to enable full bandwidth. The original repo was designed for an M.2 SSD solution, so Filip had to strip the SSD power control and define the module as a generic PCIe accessory with 8x1 configuration. To test full compatibility, Filip connected a desktop RTX 4070 GPU which only has PCIe 4.0 compatibility. Even though the GPU runs at X16 on his desktop, there was just 1-2% performance drop through the PCIe 4.0 X8 connection from the OCuLink module running on the Framework Laptop 16. It looks like performance hit is minimal on PCIe 4.0 cards, but the exact difference is yet to be determined for high-end PCIe 5.0 cards like the newer Nvidia RTX 5080 or 5090.

While Framework is taking its time with an official OCuLink module, those interested in faster speeds for their external GPU setups could soon order a working solution from Filip’s repo.