OCuLink outpaces Thunderbolt 5 in Nvidia RTX 5070 Ti tests — latter up to 14% slower on average in gaming benchmarks

External graphics enclosures have become a popular way to enhance the gaming or computing performance of thin-and-light laptops and small-form-factor desktops. However, a crucial question is which interconnection technology is the best fit in terms of performance, as there are multiple eGFX options available with Thunderbolt 3/4, Thunderbolt 5, and OCuLink connectors. Try Some Tech has tested all of them and came to a somewhat expected conclusion: pure PCIe 4.0 connectivity makes more sense. However, Thunderbolt 4 and 5 are more common.

OCuLink vs Thunderbolt 5: What is what

OCuLink (Optical-Copper Link) is a high-speed cable interface standardized by PCI-SIG to provide a direct PCIe connection between devices, generally SSDs, but more recently GPUs. Unlike Thunderbolt or USB, OCuLink avoids protocol tunneling, delivering lower latency and higher efficiency as it is essentially a native PCIe link. It supports PCIe 3.0 or 4.0 with up to four lanes, enabling bandwidth of 32 GT/s to 64 GT/s. However, while it is highly effective in terms of raw performance, OCuLink lacks mainstream adoption, is not hot-swappable, and does not support features such as power delivery, USB, or video output, which is why it is hardly used in consumer laptops. It can be used both inside and outside of desktop workstations.

Thunderbolt 4 and Thunderbolt 5 were developed by Apple and Intel for consumer devices, offering versatile, multi-protocol interfaces that utilize the USB-C connector to combine PCIe, USB, and DisplayPort functionality. Thunderbolt 4 supports PCIe 3.0 x4, offering up to 32 GT/s for data transfer. Thunderbolt 5 upgrades this to PCIe 4.0 x4, doubling the bandwidth to 64 GT/s and introducing advanced features such as 240 W charging and up to 120 GT/s for high-end displays. While both offer plug-and-play convenience, charging, and display support, they add latency due to protocol overhead. Thunderbolt 5 significantly narrows the performance gap with OCuLink, making it more viable for eGPUs, but let us check the actual results.

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The Results

When it comes to raw bandwidth, an OCuLink connection achieved a throughput of around 6.6 GB/s host-to-device and 6.7 GB/s device-to-host, significantly outpacing TB5, which achieved a throughput of 5.6 GB/s host-to-device and 5.8 GB/s device-to-host. This is a notable difference, and it will be crucial when it comes to storage and data-intensive workflows. But what about gaming?