If you have a 4K monitor and want to use additional FHD displays alongside it, the Dell D3100 provides an affordable way to connect those two or three monitors to your laptop. The $109 dock also includes five different USB ports for attaching peripherals, along with an Ethernet connector and audio jack. Users who want to connect over USB Type-C will need to buy a dongle, but otherwise, the D3100 is an inexpensive and compelling option that will work with most of today's computers.
The D3100 Docking Station is a matte-black plastic box that sits horizontally on your desk and looks just like other Dell docks, including the WD15. This one is particularly small, at 6.5 x 2.98 x 1.1 inches (the WD15 was deeper, at 6.1 x 4.3 x 0.83). The Plugable UD-3900 has a tiny base but stands 7.5 inches tall.
Dell's logo adorns the top of the dock in reflective black plastic, and the DisplayLink logo can be found on the front next to some USB ports. The bottom is covered with some nonslip rubber that will keep it in place under your monitor or behind your laptop. Unlike the WD15, the D3100's power adapter is small -- similar to what comes with your laptop -- and easy to put out of the way.
The D3100 makes great use of space and is filled to the brim with ports. The front of the dock boasts three USB 3.0 inputs -- one more than both the WD15 and UD-3900 -- and a headphone and mic combo jack. The back is where you'll find two USB 2.0 ports, the input for the power adapter, two HDMI ports and a DisplayPort for external displays, an Ethernet jack, a USB-B port for the cable that connects to laptops, and a jack for audio out.
If your monitor doesn't support HDMI, the D3100 comes with one HDMI-to-DVI adapter so you can connect that way. The dock doesn't support USB Type-C officially, but I managed to get it to work with the 2016 12-inch MacBook by adding a USB-A-to-USB-C adapter (sold separately).
The Dell D3100 was easy to set up and worked consistently. After I installed DisplayLink drivers, it simply worked. It's a nice departure from the WD15, which ditched DisplayLink in favor of USB Type-C's alternate mode. I connected a $499 Dell Inspiron 17 5000 (Core i3-5010U processor, 4GB of RAM and 500GB HDD) to the dock for testing. It isn't a powerhouse, but the average consumer may purchase it, especially at that bargain price.
The first test involved hooking up one monitor to the dock over DisplayPort, which output in beautiful, detailed 4K. Sample video featuring scenes of nature, a speeding car and trains moving in slow motion was clear and didn't stutter at all, and there was barely a dent in CPU usage.
Next, I hooked up a second 4K display over HDMI -- that one maxed out at 2560 x 1440, while the DisplayLink-connected monitor still output at 4K. (Only the DisplayLink port will drive monitors at 4K. HDMI will not.) The sample video continued to play smoothly while I used the second monitor to browse the web and typed in OpenOffice Writer on the laptop's display. The task manager suggested that using two monitors took up 3 to 4 percent of CPU resources.
With three monitors plugged in, the HDMI-connected screens dropped to 2048 x 1152 with the DisplayPort monitor running at full 4K (all in addition to the screen built into the Inspiron). It was an insane setup, and I put it all to use, running the sample video on the 4K display, using TweetDeck on another, browsing the web on the third and using OpenOffice on the actual laptop. While the video played without any issues, I noticed some intermittent performance hiccups in Google Chrome and OpenOffice when typing and scrolling. With all three displays connected, the dock consumed 2 to 7 percent of CPU resources.
The D3100 docking station doesn't support USB Type-C, but I used a USB-A to USB Type-C adapter to get it to work with the latest 12-inch MacBook, which powered all three displays with the dock. It overpowered the CPU, though, and a mix of 4K video and web browsing slowed down some animations at the operating system level, like opening and minimizing apps from the dock. If you use a USB Type-C adapter, it won't charge the laptop, so be sure to keep your power brick at the ready.
The Dell D3100 Docking Station is an affordable option that supports a 4K display as well as two other monitors to go along with it. The design is unobtrusive, and the extra USB 3.0 port is a plus. It doesn't support USB Type-C, though, so you'll need to go elsewhere (like Plugable's upcoming USB-C Triple Display Dock) for full future-proofing.
A price of $109 is a great deal for three displays, though lower-end laptops may see a few hiccups here and there. If you don't need 4K at all or just want to spend a little bit less money, you should check out Plugable's UD-3900 for $95, but that only supports two screens. Power users will want to check out the D3100 and its triple-monitor support.