Thunderbolt 3, despite not featuring on that many systems, has been a revolution for external IO. Fast enough to allow for rapid SSD data transfer or external GPU use, there’s seemingly more bandwidth on offer than anyone knows what to do with. It seems the folks behind the standard agree since the speed remains the same. That doesn’t mean Thunderbolt 4 has nothing to offer! There are a few big differences you should know about.
External GPUs have been an amazing technology on Thunderbolt 3, allowing laptops to access powerful GPUs when docked, without hauling that bulk around on the go. Unfortunately, despite Thunderbolt 3’s 40Gbps of overall bandwidth, the PCIe bandwidth is limited to 16Gbps. That has lead to high-performance GPUs hitting a performance ceiling and soon mid-range cards will face the same issue. Thunderbolt 4 doubles the available bandwidth to 32Gbps, which promises much improved eGPU performance. Of course, all PCIe over Thunderbolt devices will benefit, including hyperfast SSDs. USB 3.2 speeds remain the same at 10Gbps.
Thunderbolt 3 only supports one external display, which limits multi-monitor docked setups, Thunderbolt 4 allows for two 4K monitors, a big boon for creative professionals.
Thunderbolt 4 includes Intel Virtualization Technology for Directed I/O (VT-d). This helps ensure that only authorized users and software access devices or the computer itself over the Thunderbolt 4 connection. You can read more about how it works on Intel’s VT-d page.
Thunderbolt 3 cables are limited to only one meter in length, or the speed starts to drop. This isn’t a huge problem, since Thunderbolt devices are designed to be daisy-chained. Still, most people would appreciate a little more distance from a PC and, for example, an external monitor. Thunderbolt 4 doubles the maximum cable length to two meters.
Wake From Sleep
Thunderbolt 4 now allows the computer to be awakened by a device attached to the dock. This is a surprisingly important feature since many people use a Thunderbolt 3 dock as the entire docking station. With Thunderbolt 4 you’ll no longer have to open up your laptop to wake it up.
USB4 and Thunderbolt 4 Unified
Thunderbolt 4 is fully compliant with USB4. By the way, USB4 is really written like that, with no space between “USB” and “4”! Anyway, if you plug a USB4 (or older) device into a Thunderbolt 4 port, it will work exactly as its supposed to. The reverse is not true, while every Thunderbolt 4 port is a USB4 port, USB4 ports are not Thunderbolt-compatible. So devices that are Thunderbolt-only won’t work in them.
Worth the Upgrade?
If you’re using a desktop system and have open PCIe slots, it may well be worth installing a Thunderbolt 4 expansion card. It will provide an instant boost to any PCIe peripherals you’re using and of course, you can now also add one additional monitor.
If you need to buy a new laptop or an entirely new motherboard, it’s probably not worth the improvements of Thunderbolt 4, but when you next have to buy a new computer it’s certainly worth picking one that offers Thunderbolt 4, which opens up access to much better PCIe peripherals and will also get you ready for the flood of USB4 devices on the horizon.