Plugable UD-6950PDZ review: Need three 4K displays? Buy this USB-C dock

Three displays? Three? If you’re the type of person who takes a maximalist approach to displays, then the Plugable USB-C Triple 4K HDMI and DisplayPort Display Docking Station (UD-6950PDZ) is for you. This DisplayLink USB-C dock gives you the power of Thunderbolt, but without the cost — and some features.

You might consider the Plugable UD-6950PDZ to be the larger cousin of the Plugable UD-6950PDH, a double-display docking station that we reviewed previously. Neither the UD-6950PDZ nor the UD-6950PDH are “true” Thunderbolt docks. Instead, they both use the DisplayLink protocol, which approximates Thunderbolt capabilities but uses the DisplayLink drivers and protocol as a means of data compression. The difference between the two is that the UD-6950PDH routes two displays over this bus, while the UD-6950PDZ that we’re reviewing here connects three displays instead.

A selling point of many, though not all, Plugable docks is the inclusion of more display ports than you could ever want. Most docks ask you to choose between DisplayPort and HDMI, or even use a direct Thunderbolt connection. Plugable offers both: On the back of the UD-6950PDZ dock are three sets of DisplayPort 1.2 and HDMI 1.4/2.0 ports, so that you can use whatever displays and cables you have on hand. That’s way more flexibility than anything else on the market. There are also four more 5Gbps USB-A ports.

The Plugable UD-6950PDZ offers just two 5Gbps USB-A ports on the front of the dock, along with a 3.5mm mic/headphone jack. A Kensington lock slot is mounted on the side.

The dock is made from plastic, with venting on the bottom. It became warm under load, but not to worrying levels.

Further reading: See our roundup of the best Thunderbolt docks, which includes USB-C DisplayLink docks, to learn about competing products.

Mark Hachman / IDG

Some words about DisplayLink

DisplayLink docks are not a “cheap” version of Thunderbolt. Instead, they’ve proven to be a stable, inexpensive alternative to a Thunderbolt dock, enough that we lump them into the same category. They do lack the raw horsepower of a 40Gbps Thunderbolt dock, operating over a 10Gbps bus instead. On the other hand, driving displays tends to consume the bulk of that bandwidth — exactly what DisplayLink was designed to offset.

It’s even weirder: Plugable says that the 3-foot cable between its dock and your PC runs at just 5Gbps, and somehow squeezes three 4K displays worth of data over that. Black magic! The included cable was stiffer than I’d like, however, with not much tolerance for my laptop’s USB-C port. It almost felt like I was forcing it into the slot.

This dock is powered by the Synaptics DL-6950 chip, which incorporates what the company calls DL Compression 3.0, which does a better job adapting to the demands of what you’re seeing on screen. What the UD-6950PDZ does is use the DL-6950 chip to form two sets of either an HDMI 2.0 or DisplayPort 1.2 connection, as well as use your laptop’s ability to directly drive HDMI or DisplayPort over a third channel. It’s confusing! Essentially, the dock is doing two-thirds of the work to enable three displays, with your laptop contributing the other third. As with most docks of this type, your experience will benefit from a modern laptop.

That the Plugable UD-6950PDZ serves a fairly small niche shouldn’t undersell what it can do: Crowding three 4K displays onto your desktop is still impressive.

The Plugable UD-6950PDZ is also dependent on your PC. If your PC’s USB-C port can output DisplayPort 1.4, the dock will support a 4K display at 60Hz. If it only supports DisplayPort 1.2, 4K30 is the maximum resolution it will support. Unfortunately, this can be one of the frustrating things about a DisplayLink or Thunderbolt dock, as it’s dependent on features that often your laptop maker doesn’t necessarily highlight.

Mark Hachman / IDG

How well does the Plugable UD-6950PDZ work?

On our test laptops, the Plugable UD-6950PDZ supported three displays: a 1440p widescreen at 100Hz, and two 4K displays running at 60Hz. (The dock’s display outputs aren’t actually locked to a particular resolution; it’s just that the available bandwidth is best suited to multiple displays at certain fixed resolutions.) I tried multiple configurations and cables, and it doesn’t seem to matter whether I used a DisplayPort or an HDMI cable, and where I plugged it in — the output was the same.

If you’re working in email, or Excel, or a web page with unmoving, fixed content, you should be absolutely fine with this dock.

Don’t push it too hard, though. One of the tests we perform plays back a 4K YouTube video, just to see what YouTube’s algorithm will deliver. The dock also played back Netflix videos on all three screens, proving that DRM didn’t interfere.

The actual YouTube resolution (measured by YouTube’s “viewport” description) was less than what we expected, varying between a bit under 1080p resolution and 1440p depending on the setup. Hardly any frames dropped. However, there was some slight, noticeable choppiness in how the frames played back that could prove to be annoying.

We saw something similar with our storage tests. Running PCMark’s storage benchmark, we recorded about 10MB/s less bandwidth (120.79MB/s) than other docks we’ve tested, which isn’t bad. But when we tested the storage benchmark while streaming our test video, the video dropped 234 out of 10,000 frames, which is a lot more than we’d hope for. That’s definitely noticeable.

When two displays is enough

Plugable UD-6950H USB 3.0 Dual 4K Docking Station

Best Prices Today: $179.00 at Newegg | $179.00 at Walmart

There’s another catch: There are no USB-C ports at all, which means that this dock isn’t a great solution for charging a smartphone from the most common USB-C chargers. Don’t worry about buying an adapter, either: the USB-A ports only supply 2.4W by our measurements, enough to only slow-charge a smartphone over several hours.

The Plugable UD-6950PDZ also supplies a bit less power than other docks, a rated 60W that works out to 56.7W on our tests. That’s perfectly fine for a productivity laptop, but if your laptop has a discrete GPU that’s active, or if you have it running in a high-performance mode, the port may not supply enough power to charge it while on the dock. (In that case, the laptop will drain power, albeit more slowly than if it were running solely on battery.)

Our conclusion? This is a niche dock for those who need three displays. Otherwise we’d lean towards the dual-display version, the Plugable UD-6950H, at a slightly more affordable $200 or so. We also miss the lack of smartphone charging, though it’s not a deal-breaker. What the Plugable UD-6950PDZ accomplishes is impressive, though it has its limits.