Dual Computer, Dual Monitor with KVM

The Challenge

These days, it’s pretty standard for IT folk to be working from home most of the time. If you’re anything like me, you’ll have a home computer (or maybe a few!), and a work laptop. Your home computer will likely have a couple of monitors attached, along with a keyboard and mouse that you really like.

Wouldn’t it be nice if you could use your nice home screens, keyboard and mouse, when you’re using your work laptop? And wouldn’t it be nice to be able to easily and painlessly switch between your work laptop and your home machine?

The Answer

Of course you can! You just need a KVM switch! The technology is nothing new. Especially in the corporate environment and in data centres. But it’s not all that common in the home office environment. So here I’ll describe what I’ve done, in case it helps you solve a similar challenge.

What’s KVM Switch?

This technology dates back to the 90s. KVM is short for “Keyboard, Video, Mouse”. Originally, you would attach one keyboard, one mouse, and one monitor, to the KVM. And then you’d attach multiple computers, depending on how many devices your KVM supports. Then you can switch between those devices, by pressing a button.

These days it’s common to have KVM switches that support extra features like…

• Multiple monitors.
• Audio input/output.
• Extra USB ports, i.e. to attach USB devices to the switch, allowing these devices to be used by whichever computer is currently active.

My Setup

My connectivity looks like this:

A few notes about this:

• My KVM switch:
  • Supports two connected machines.
  • Has 4 input HDMI ports; 2 per connected machine. (You can KVM switches that support other types of input, e.g. VGA, DVI, DisplayPort, etc. But I wanted HDMI.)
  • Has 2 output HDMI ports, in order to connect to two monitors.
  • Has 4 front USB ports, for keyboard, mouse, and two other USB devices.
  • Has 2 rear USB ports, to route the keyboard/mouse/audio signal from the KVM to the connected devices.
• My desktop has a graphics card with multiple output ports. Here, I’ve used two HDMI ports on my graphics card. Each graphics card port is connected by an HDMI cable to an HDMI input on the KVM.
• My work laptop has only a single HDMI output port. But it also has a USB-C connector which can send output video signal. So I bought an adapter that can convert from the laptop’s USB-C to HDMI. Then I connect the adapter to the KVM, using an HDMI cable. In total, there are two HDMI feeds going from the laptop to the KVM.

And it looks like this…

Notes about the KVM itself:

• I can switch between the desktop and the laptop by pressing the “Select” button. (This KVM actually has a remote that you can attach to do this. This is useful if you want to hide your KVM away.)
• I have connected wireless mouse and wireless keyboard to two of the USB ports.
• In the end, I haven’t routed the 3.5mm audio through this KVM, as I found it seemed to be generating a lot of interference through my speakers. (Edit: there is a fix for this! See later…)

The Kit I Purchased

• This Nepzol 2 Monitor (HDMI) / 2 Machine KVM switch with built-in USB hub.
  • This works pretty well, and was easy to set up.
  • It’s a pretty good price. You can pay a lot more.
  • It comes with 4 HDMI cables, as well as the required USB cables. So that’s a plus.
• This KiWiBiRD USB-C to HDMI 4K Multiport Adapter HUB with USB 3.0, USB-C Powered Delivery (Fast Charging)
  • This also worked straight out of the box and allows me to connect from my laptop’s USB-C port to the KVM’s HDMI port.
  • Because the adapter also has USB-C PD, this means I can connect the laptop’s dedicated USB-C power supply to the adapter, so I don’t need to consume an extra USB-C port on the laptop itself.

The Audio Interference Fix

The vendor of the KVM was very prompt in responding to my query about audio interference. I was plugging my 3.5mm audio lead to my speakers into the KVM. The vendor explained that audio interference in this configuration is common. They recommended plugging my external speakers into the 3.5mm audio out from my monitor instead. And since the monitor is already connected to the KVM with HDMI, there’s no need for any 3.5mm connectivity to the KVM itself. This worked a treat, so now I can use my external speakers/sub with both devices.