Saturday, 22 Sep 2018

Cracking open the CalDigit USB-C dock

As promised earlier in our preview of this dock, here we are with a full review of the CalDigit USB-C dock. As we wrote earlier, we were positive on first impression, notably the ease of use and the build quality. So how does it look like?

Let’s have a look at the feature list. When compared with the smaller hubs, the number of ports is impressive. Having used it for two weeks, we can confidently say that this dock fully delivers on the USB-C promise of hooking up a single cable. That’s due to the number of ports: basically everything you’d want is included — even audio. So when normally, we’d have to first connect the hub and then our Sennheiser headphones to the laptop, our cans are now always in the dock its front 3.5mm audio port.

Video ports

There are two video ports on the dock, HDMI and DisplayPort. This makes you think about using two displays with this dock. However, the CalDigit product page states that it depends on the laptop hardware: “For Mac customers looking to use dual monitors with an extended desktop this is not currently possible, as MST (Multi Stream Transport) is not supported within the Mac OS.” We weren’t able to test with another OS in time for this review, but will follow up when we have the chance.

Out of the box, the DisplayPort 1.2a port supports up to 2560×1440 resolutions, and the HDMI 2.0 port supports resolutions up 4K.

We always make a specific mention for people with 4K monitors: you hit the inherent USB-C limitation of a refresh rate of 30Hz. As mentioned in our other tests, we don’t advise 30Hz in daily usage, because quick window animations may not appear as fluently. However, some people don’t much care about this — myself included.

CalDigit offers an alternative firmware version that divides the available bandwidth in a different way: it switches the USB 3.0 ports to USB 2.0 speeds, and the video ports will now support 60 Hz refresh frequency. We wish this weren’t necessary, but the current USB-C limitations are to blame. At least it’s a solution.

Data transfer

We always test if there’s a performance difference between copying to a drive without and with the dock in between. We tested this with a Samsung 128 GB SSD. We did not encounter any problem; we ran the test a couple of times and took an average result. As you can see, with the dock in between, the write speeds are slightly lower. This is consistent with other docks we have tested.

We did not encounter any WiFi interruptions or degradation when transferring data over the dock. Note that since all ports are USB 3.1 gen 1, the maximum transfer speed is 5 Gbps. In other words, the theoretical maximum is 640 MB/s; hooking up a RAID array of SSDs will put the bottleneck at the dock.

Ethernet port

CalDigit USB-C dock iperf
The ethernet port is not just nice; we think it’s a necessity for equipment that’s sold as being a dock. Some workplaces have a policy that a wired network connection is required for access to the company network. Using the dock’s ethernet requires you install a driver from the CalDigit site. No big hassle, but we still prefer a driverless installation. The reason is probably that all chips used in the dock are made by Cypress. Thus engineering-wise, integrating their ethernet IP core is probably easier and more cost efficient. The gigabit network adapter performed good enough (tested with IPerf):

Power Delivery

The dock comes with a beefy 90W charger. Of that 90, the specs say it should be able to deliver 60W to the USB-C port to the laptop, or 36W if a device is connected to the front USB port. According to the System Information app on our Late 2016 15″ MacBook Pro, this is correct; the laptop detected a 60W charger if nothing is connected to the front USB port, or 36W otherwise. And that’s what we have measured as well. Now USB-PD is a finicky beast, so different laptops may give different results.

Front charging port

That said, we’ve tested this dock for two weeks and our normal power usage hovers around 26-28W. This means that if we peg the CPU and/or GPU, the laptop will hit the battery. During regular usage, you will not notice this. If you plan on encoding videos, then it’s better to use the power supply that came with the laptop.

As for device charging, the specs mention that the front USB port is able to deliver 10.5W. This is incredibly useful when you regularly connect a tablet; it charges quickly and can be used heavily without depleting the battery or reducing the charging speed. Now we fully trust marketing material but always double-check it. In this case, we weren’t able to get that wattage with our 9.7″ iPad Pro, which pulled a maximum of 6W over the USB port.

Build quality

When considering build quality, there’s a major difference between this dock and the hubs we tested so far. The hubs are meant to be portable, and are as light as possible, to the point of feeling flimsy. This is not the case with this dock: it feels hefty and it’s definitely designed to stay put. For example, this means that you can single-handedly plug in your headphones.

The case has the typical CalDigit look and feel: a thick, ribbed aluminum case that feels solid and can efficiently radiate plenty of heat. It has a matte finish. The dock gets warm but not hot.

Opening it up

We were able to crack open the dock and take a peek inside.

As you can see, opening is very easy. The screws at the side are covered with an aluminum strip that’s fixed with some tape, and it’s easy to peel off. Three screws later and you’re able to slide the dock out of its casing. The PCB is covered with a thin lid, with three elastomer strips for grounding. After removing the lid, we’re gratified with a look at the PCB (click to enlarge).

So let’s zoom in and find out what’s on there:

  1. IC with marking CYUSB3328-88LTXC. This is a USB 3.0 hub from Cypress. It has support for USB Battery Charging 1.2. Curiously, only one port (the front one) delivered a higher current when we tested charging. We’re not sure why the other ports don’t support this, as the data sheet says that it can provide this for all ports — perhaps this restriction is in place to limit the total power consumption of the dock.
  2. IC with marking CYUSB3610-68LTXC again from Cypress. The full product name is EZ-USB GX3 SuperSpeed USB 3.0 to Ethernet Controller. Thus, this IC provides the ethernet port on the back of the dock. What’s interesting, is that the product description mainly touts it as a way to make USB-C dongles.
  3. DisplayPort splitter STDP4320. This IC provides the MST (Multi-Stream Transport) capability. In other words, if your laptop provides MST on its USB-C port(s), then it basically mushes together two DisplayPort signals onto that single port (this is called multiplexing). This IC demuxes (de-multiplexes) these signals, splitting them over the two video ports of the dock.
  4. DisplayPort to HDMI 2.0 MCDP2850BC. This IC transforms a DisplayPort signal into an HDMI port.
  5. A pair of CYPD1122-40LQXI from Cypress; full product name is EZ-PD CCG1 Type-C Port Controller. These control the two USB-C ports on the back of the dock, including the power delivery.

Board markings in the middle (“CY”) indicate that not only components but probably also PCB design came from Cypress. What many people don’t know, is that this is a company with a pretty friendly face. Search on YouTube for “Cypress USB Type-C” and you’ll find a number of educational videos.

Miscellaneous and what’s not on there

Personally, we don’t know anyone who still uses a SuperDrive. But if you still have one, you’ll be happy to know that you can hook it up to this dock without any problems.

What’s not on there: there’s no SD or micro-SD card slot on this dock, nor are there any of the more exotic/legacy ports like FireWire 800 or eSATA.


We very much like this dock for its design, ports and component choice (Cypress). This dock is not for you if you regularly use SD cards; get the OWC Thunderbolt 3 dock that’s coming out soon (for double the price) or simply hook up any of the cheap little card slot dongles that are available. Also, we would have preferred that the charging speed of the laptop would not drop from 60 to 36W when the front USB port is in use. But considering the price of the dock (as we write this, US$150), it’s already quite amazing. The USB device charging capabilities and the many ports on the dock make it a good choice. It fully delivers on the promise of USB-C to just connect one cable and start working.

Available on Amazon, or check our other recommendations.

Caldigit provided the dock for this review. (We’re not yet sure how they feel about us cracking it open.)