Discussion

Display setup

sequenceDiagram;
    participant eGPU
    participant CPU
    participant USB 4 dock
    participant 1080p monitor
    CPU->>eGPU: Oculink PCIe TX
    eGPU->>CPU: Oculink PCIe RX
    CPU->>USB 4 dock: 40Gb/s USB 4 cable
    USB 4 dock->>1080p monitor: HDMI cable

Benchmark output display is connected to a USB 4 dock (40Gb/s) and has a resolution of 1080p.
This means Oculink PCIe connection has to be stable in both the transmit and receive direction.
When eGPU data comes back to CPU it actually goes through the integrated AMD 680m based on copy activity in task manager.

Flexible PCB and single board design

❮

❯

Both the flexible PCB multi-board design and single board design achieved PCIe 3.0 speeds.
Their results across all synthetic benchmarks were identical.
PCIe 3.0 connection was stable and bandwidth reached theoretical values.
PCIe 4.0 could not be achieved at all.

Aliexpress PCIe 4.0 adapters

❮

❯

Both the adapters that came with the Adtlink eGPU and the silver plated 12cm adapter reached PCIe 4.0 speeds.
PCIe 4.0 connection was stable and bandwidth reached theoretical values.
Performance uplift from PCIe 3.0 to PCIe 4.0 in this setup is significant.
Bandwidth limit from eGPU to CPU limits the number of frames that can be sent to display.

Synthetic benchmarks Conclusion