A Lenovo X1 Tablet is a marvel of engineering in terms of packing a lot into a small space. But it’s so small, there are very few external connectors: one USB-C which also functions as a power supply port, one USB 3.0, and one mini DisplayPort. To use this machine as a desktop replacement, you need a dock. Turns out, not all docks are created equal.
To make a long story short, I bought a USB-C dock (40A9), had lots of problems with it, returned it, and got a USB 3.0 Pro dock (40A7) instead.
The two monitors that I want to run through the dock are a Dell U2410 (1920×1200 @ 60Hz) and an old SyncMaster 213T (1600×1200 @ 60Hz).
Here’s my experience in tabular form:
| USB-C Dock 40A9 | USB 3.0 Pro Dock 40A7 | |
| Supports my two external monitors | No, max two @ 1920×1080. Connecting both my monitors caused flickering on and off. | Yes, max two @ 1920×1200 |
| Computer can boot with dock attached | Often hangs on red “Lenovo” screen | Yes |
| Allows monitor connected via DisplayPort to sleep | No, Dell monitor kept waking up every few seconds; had to manually turn off monitor when not in use. | Yes |
| Allows PXE boot from wired network adapter | Yes | Yes |
| Allows AMT vPro control from wired network adapter | No | No |
| Combines power supply and data connection in one cable | Yes; leaves USB 3.0 jack on computer open. | No; requires discrete power supply for computer plus the use of the tablet’s only USB 3.0 jack. |
| List Price (U.S.) | $199.99 | $179.99 |
| Price on Amazon (U.S.) | $113.41 New | $75.88 Used – Very Good |
Note that there is also a USB 3.0 Ultra dock (40A8). Compared to the USB 3.0 Pro, the Ultra has an extra USB port and substitutes HDMI for the Pro’s DVI video port. My older monitor has DVI but not HDMI, so the Pro dock was actually a better match (though it does require that I use an extra external USB hub, which is working fine).
The USB-C is a nice idea especially with being able to supply power and data through one cable. But in practice, it falls short. The USB 3.0 Pro dock, based on the widely-used DisplayLink hardware and drivers, looks like it will be the more capable and reliable choice.