A new interface is on the horizon

Thunderbolt has long been the top choice for fast interconnection between computers and peripherals. It can perform multiple operations and carry multiple standards over one cable, including DisplayPort, USB, Power Delivery, and PCI Express tunnelling. It's also very fast, with current speeds reaching 40Gbps and future speeds going to 80Gbps and 120Gbps in Thunderbolt 5.

USB-C is the main connector for Thunderbolt, and the majority of features mentioned above, including standard USB-C without Thunderbolt, can do too, with the exception of PCI Express tunnelling. 

USB4 came into the mainstream with the introduction of the MacBook Pro M1 2020. On paper, USB4 seems to be the same as Thunderbolt, with only a few subtle differences. The first of those differences is that when it was released, it wasn't exclusive to Intel (Thunderbolt is no longer exclusive to Intel and Apple devices but is now starting to appear on devices by others, such as AMD). USB4 is also royalty-free, making it cheaper than Thunderbolt. The main issue and why USB4 hasn't supplanted Thunderbolt is that it is less stable and permits cabling to be of poor quality. In addition, one of the things I dislike the most about USB4 is that it's not always clear what features a port may implement, whereas with Thunderbolt, it must meet specific requirements. Lastly, cables and ports could only be 20Gbps certified and it's not always apparent without delving into detail about the device to discover the speed.

While Thunderbolt and USB4 continue to dominate the market, a new challenger has quietly emerged: OCuLink. Originally developed as a means of connecting PCI Express devices externally, OCuLink does not attempt to be a replacement for USB. Instead, it focuses on doing one thing exceptionally well: providing direct access to PCI Express lanes.

At first glance, OCuLink appears to be taking a step backwards. It cannot carry DisplayPort, it cannot provide USB connectivity, and it cannot deliver meaningful amounts of power. Unlike Thunderbolt, which attempts to be a universal connection standard, OCuLink is highly specialised. However, that specialisation is exactly why it is becoming increasingly attractive.

The biggest advantage OCuLink has over Thunderbolt is performance. While Thunderbolt tunnels PCI Express traffic through additional layers of abstraction, OCuLink provides a more direct connection to the PCI Express bus itself. This reduces overhead and allows devices such as external graphics cards (eGPUs) to perform significantly closer to how they would if they were installed internally.

This has made OCuLink particularly popular amongst enthusiasts and manufacturers of handheld gaming PCs. Devices such as the GPD Win series and other portable gaming systems have begun to incorporate OCuLink ports specifically to support external graphics cards. When paired with a desktop GPU, these small handheld devices can suddenly transform into capable gaming workstations.

Another advantage is cost. Thunderbolt controllers add complexity and expense to a device. OCuLink, by comparison, is relatively straightforward to implement because it is effectively exposing PCI Express lanes externally. For manufacturers looking to provide high-performance expansion without paying for Thunderbolt certification or additional controller hardware, OCuLink can be an attractive option.

There are drawbacks, of course. OCuLink is far less user-friendly than Thunderbolt or USB-C. The connectors are bulkier, less familiar to consumers, and often require separate power solutions for connected devices. It also lacks the versatility that has made USB-C so successful. You cannot connect your monitor, charge your laptop, and transfer files through a single OCuLink cable. If you need those features, Thunderbolt remains the superior choice.

There is also the question of adoption. Thunderbolt and USB-C have benefited from widespread industry support and have become commonplace on laptops, desktops, monitors, docking stations, and peripherals. OCuLink currently exists primarily within enthusiast circles and niche products. Whether it can move beyond that audience remains to be seen.

Personally, I do not believe OCuLink will replace Thunderbolt or USB-C. The two technologies solve different problems. Thunderbolt excels as an all-purpose connectivity standard, while OCuLink focuses on providing the fastest and most direct external PCI Express connection possible. Rather than being competitors, they may ultimately complement one another.

What OCuLink does demonstrate, however, is that there remains demand for uncompromising performance. As handheld gaming PCs, compact computers, and AI workloads continue to grow in popularity, there will always be users willing to trade convenience for speed. For those users, OCuLink may prove to be one of the most interesting connectivity standards to emerge in recent years.

Whether OCuLink becomes a mainstream success or remains a niche enthusiast technology, one thing is clear: for the first time in many years, Thunderbolt has a challenger that offers something genuinely different.