CalDigit Thunderbolt 3 Mini Dock (Dual HDMI 2.0) (TB3-MiniDock-HM)
Out of the box, the CalDigit Thunderbolt 3 Mini Dock (Dual HDMI 2.) seems ideal for a purpose-built, bus-powered Thunderbolt dock: rather inexpensive, with just the ports you’ll need and not much else.
The version we reviewed ships with gigabit ethernet, a pair of USB Type-A ports (USB 3 and USB 2) and two HDMI 2.0 ports. A shortish 5.3-inch Thunderbolt 3 cable connects the bus-powered TB3-MiniDock-HM to your laptop. Remember, “bus-powered” means that you don’t need a charging brick, saving space.
Our test laptop began unexpectedly reporting glitches, however, including visual errors on both displays and the inability of the laptop to read USB drives or connect to a USB mouse—until we discovered that the power cable had worked loose. CalDigit diagnosed the problem as our laptop’s inability to supply the requisite 15W of power for the Mini Dock to function appropriately. (The Mini Dock does not include a charging port, and we’ve seen other users complain about the USB-A issue.) The Mini Dock again worked when we attached the laptop's charger, but subsequently failed to recognize an external USB drive. It seems like not enough power is consistently passing through the USB-A ports, based on our tests with a USB-C power meter. We tested the dock on a second Thunderbolt-powered laptop and received the same result.
Performance-wise, the Thunderbolt 3 Mini Dock performed well, though with numerous frames dropped on our two 4K/60Hz test videos. Heat was never an issue.
OWC Thunderbolt Dock (OWCTB4DOCK)
The big brother to OWC's Thunderbolt Hub, the OWC Thunderbolt Dock provides three Thunderbolt 3 ports for Thunderbolt devices, plus three USB-A 10Gbps ports, one USB-A 2.0 charging port, an SD (UHS-II) card slot, gigabit Ethernet, and an audio jack.
Like its smaller sibling, this is a specialty dock is designed for those who have invested in Thunderbolt displays and other Thunderbolt devices. There are no external display connections besides the Thunderbolt interface. The Dock measures 7.8in. x 2.9in. x 1.0in. and 14.1oz. The included Thunderbolt 4 cable measures about 2.5 feet.
Like the OWC Thunderbolt Hub, the Dock supports direct connections to Thunderbolt displays and devices, including a pair of 4K/60 displays. (The Dock supports DisplayPort 1.4.) If you connect another Thunderbolt dock to one of the Thunderbolt 3 outputs, however, only one 4K/60 display will be enabled. Directly connected, a Thunderbolt 4 drive wrote data at 1,221 MB/s and read at 2,292 MB/s. Connected to the Dock, it wrote at 1027 MB/s and wrote at 2210MB/s. An SD card placed inside the Dock read and wrote data at speeds comparable to an SD card slot built into Microsoft's Surface Book 4 laptop.
OWC says that the Dock supplies up to 90W for charging the host laptop. OWC doesn't define the charging capabilities of the "charging" USB 2.0 Type A port, but we measured it at about 7W, enough to charge, but not fast-charge, a OnePlus smartphone. The Dock remained absolutely cool to the touch under load.
Thunderbolt dock buyer’s guide
If you’re on the fence about whether a Thunderbolt dock is right for you, knowing the answers to the following questions could help you.
How do I know if my laptop has Thunderbolt?
The short answer: Look at the laptop’s published specifications to be sure. A Thunderbolt will look indistinguishable from a USB-C port. Or put another way, all Thunderbolt ports are USB-C, but not all USB-C ports are Thunderbolt-equipped.
Thunderbolt ports are supposed to have a small lightning-bolt icon to identify them. But some laptop makers use a similar lightning-bolt icon to indicate that a USB-C port can be used for charging your phone, and not for Thunderbolt. Laptop makers sometimes don't want to clutter the clean lines of their products by adding additional logos, it seems.
Adding to the confusion, you may also see USB-C hubs marketed as “Thunderbolt compatible.” That’s true. You can plug a Thunderbolt dock into a non-Thunderbolt, generic USB-C port. But it will be limited by the available bandwidth that the port provides, so it’s somewhat deceptive in that regard.
How fast is Thunderbolt?
Most USB-C ports are built on the second-generation USB 3.1 data-transfer standard, which transfers data at 10Gbps. Most Thunderbolt 3 ports, the most common standard, transfer data at 40Gbps.
There are somewhat rare exceptions: A new USB 3.2 Gen 2X2 spec can pair two 10Gbps channels together, creating an aggregate 20Gbps hub. And while the vast majority of Thunderbolt 3-equipped laptops are designed with four PCIe lanes for a total of 40Gbps, some laptops only ship with two PCIe lanes for a total of 20Gbps. (A Dell support page, for example, details its four-lane and two-lane laptops.) Essentially, a 20Gbps connection should be enough for a single 4K monitor running at 60Hz, with a bit of extra bandwidth for other data transfers among connected peripherals.
Thunderbolt 4 has been announced, and the spec will be part of the first laptops shipping with Intel’s Tiger Lake chips. While it’s backwards-compatible with Thunderbolt 3, we haven’t seen any Thunderbolt 4-specific docks yet.
What to look for in a Thunderbolt dock
Ports, cables, peripherals: Those are the three major considerations when buying a Thunderbolt dock.
Consider what peripherals you own, or plan to buy. Do you want a basic Thunderbolt dock, with just a pair of HDMI ports for connecting two displays? Does an SD card slot matter? How many USB Type A peripherals do you plan to attach? Do you want to use the Thunderbolt cable to charge your laptop, too? Some Thunderbolt hubs have two Thunderbolt ports on them: one for communicating with the laptop, and an additional one for daisy-chaining another Thunderbolt dock or, alternatively, a USB-C hub for additional, unplanned I/O needs. This may be overkill, or maybe not.
Cables can be an unexpectedly important consideration, too. Virtually every dock ships with a Thunderbolt cable. You may already own a pair of 4K monitors with HDMI and DisplayPort port options, but connected via two HDMI cables. Unfortunately, not every Thunderbolt dock will accommodate your setup, as a few included just one DisplayPort connection and one HDMI port. (Don’t worry: a convenient braided DisplayPort cable costs about $10 or so, about the same price as a braided HDMI cable. Look for the appropriate length.) Some Thunderbolt docks replace either HDMI or DisplayPort with an external USB-C port instead, planning ahead for a future where pricier displays use the DisplayPort protocol running over a USB-C cable.
Check your laptop’s power supply. If the Thunderbolt dock supplies power, is it enough? If it’s not, your laptop may pop up a warning. The terminology differs, too: a “bus-powered” dock won’t come with an external charger in the package, saving some cost, space, and power concerns. A dock with “power delivery” will supply its own power and charge your laptop and/or a phone via your laptop’s existing USB-C charger. (Chances are that it won’t offer the quick-charging capabilities premium smartphones offer, though.) Check your laptop’s charger to learn how much power it supplies (and how much the dock will need to supply to replace it) and whether it uses a USB-C connection. If so, the dock may replace it.
There’s one more consideration: the length of the Thunderbolt cable between your laptop and the dock itself. You may have noticed or heard about USB-C ports wearing out on smartphones; a loose or wobbly connector on Thunderbolt docks can cause monitors to unexpectedly flicker or lose connection. Consider how much tension will be put on a cable given its length and intended location and save yourself the potential for frustrating troubleshooting. (Is it the laptop? The Thunderbolt cord? The dock itself? A peripheral? The peripheral cable?).
How we tested
We’re working from the premise that you’re buying a Thunderbolt 3 dock for its unique ability to connect to two 4K monitors at 60Hz. Our first test simply connected each dock to a pair of 4K/60Hz displays, each of which could accept DisplayPort and HDMI cabling, and made sure there were no visual artifacts at 60Hz resolution.
Second, we checked to see whether the available ports delivered the bandwidth we’d expect, connecting them to an external SSD and transferring a collection of test files over the Thunderbolt cable and port. We also used AJA’s System Test tool to double-check our numbers and test whether read and write speeds were consistent.
Finally, we spot-checked the available power draw of the hubs and ports with a USB power meter, as well as simply connecting them to bus-powered devices to see if they could deliver enough power to allow them to operate. Here, we discovered that one of our testing laptops didn’t supply enough power running on battery to power a bus-powered Thunderbolt dock, so we enlisted a second, different laptop as a backup.
This story was updated on June 4, 2021 with new information and product recommendations.