USB C dual monitor KVM switch: A Practical Solution

Adapters, cables, KVMs are tricky - you only know if it works after purchasing but will never know how long it will last for. Things get even worse with the propagation of USB Type C ports, due to confusing port/cable specs. Here, I provide a step by step DIY solution to help you find the best way to share two monitors between your work/home/laptop/PC/Macs.

A practical pipeline

1. What are the resolutions, frame rate, and ports of your monitors? Know the limits of your computers. Do they support the resolution/frame rate of your monitors? Know the cables required to achieve the resolution/frame rate.

• Mac OS do not support 8K or >60 Hz frame rate at the time of writing. HDMI 2.1 cable is required to transmit 4K 120Hz. Does your monitor support DP Daisy Chain?

2. Do your computers support two monitors? If so, how? List all the possibilities to drive two monitors with your computers.

• Newer Windows may allow driving two monitors with one USB C port under specific setup. For Apple silicon Macs, all pro modles (Pro and Max chips) can support two monitors via two USB C ports. M1/M2 Macs can drive two monitors in two ways: (A) by using a USB C port and a HDMI port; (B) use software based DisplayLink Graphics.

3. Learn the basic methods. Generally there are three ways to do a monitor switch which I list as questions here: (A) What is a KVM switch? What are the inputs and outputs for dual monitor KVM switches? (B) What are HDMI switches? (C) What is a Thunderbolt/USB3.2 Type C bi-direction switch?

• CKL makes multiple models of 2 in 2 out KVMs including on with a USB C and HDMI inputs CKL-622TH-M. These all-in-one KVMs are hands-down the best solution. However, they can get really pricey when it comes to USB C. Buy from a trusty source so that you get a warranty. I do not recommend buying expensive all-in-one units since when they stop working you loss all the $$. If you are okay with making some compromises (see #5), a combination of HDMI switch, USB C switches, and monitor inputs may be a more economic solution.

• Other things to take into consideration includes: How tow switch other peripherals? How to charge laptops?

4. Sketch out solutions. Grab your favorite pen and paper and figure out some solutions. You may come up with new methods while sketching.

• I’d recommend to start from “bottle necks” or you’ll encounter countless methods. For example, one of your computers may only support dual monitors using 2 separate ports, just start with using two ports for the other computer as well since this makes things much easier.

• If you are using a USB C hub to connect peripherals and want it to be switched between computers, it needs to be connected to USB C source, which means there are only two options: (A) connect it to a USB C switch to switch between two PCs; (B) connect it directly to PCs and manually swap connections. In either way, one of the monitors will have to get signal from the hub. Make sure the hub is capable of outputting the resolution/frame rate you need.

5. Determine the compromises you’re willing to take for the act of switching monitors. Are your willing to manually switch an input on the monitor? Or even unplug and re-plug a cable? Can you bear with 10-20s of wait between switches? What about 20-30s? How many buttons are you willing to press to make the switch (1 or 2 or 3)?

• Using KVM switches with MacOS is slow - typically in the 10-30s range. This can be speed up by using HDMI switches or USB C bi-direction switches.

Some notes

In the list above, 1-3 are the things that you’ll have to do research on. The questions I listed should cover most things you need to know. Avoid going down rabbit holes like differences between various USB 3.x Gen x and Thunderbolt; BUS of USB pots on Macbook etc.

In the end, you’ll come up with several methods. Before buying new equipment, make sure you test them on individual computers. Things that work on paper may not work in real life.

Lastly, ask yourself if you really need the best parts, like an 8K HDMI switch. Yes they are future proof, but things will always be cheaper in the future. I’d suggest only buy the parts that match the specs you need.

I recommend buying from trusty brands, such as Cable Matters, Sabrent, CalDigit etc.

My setup

I swap monitors between an M1 Mac mini and a M1 Pro Macbook Pro. Which means I’ll have to use two cables as video inputs for each computers. Here’s my solution:

1. Monitor1 is connected to each computer individually via HDMI.
2. Monitor2 is connected to a USB3.2 Type C switch, which is then connected to each computer via USB C 3.2 cables.
3. I added a Caldigit Tb4 Element Hub (that I originally own) between Monitor2 and the hub, which allows me to plug all my peripherals. This is not necessary because my Monitor2 also supports USB C input and can be used as a USB hub.
4. Power delivery is achieved by the USB cable directly plugged into the laptop, which comes from the USB switch, which is capable of passing over power delivered by my hub.
5. Because the laptop does not live on my desk, I’m fine with plugging in two cables every time I want to use it with my monitors. To avoid plugging in cables, adding a cheap HDMI switch for Monitor1 does the job.

Good luck finding your piece.