How to Set Up a 4-Port HDMI KVM Switch? | Match Port Numbers

Setting up a 4-port HDMI KVM switch works best when each computer’s HDMI and USB cables plug into the same numbered port on the KVM.

Most 4-port KVM setups fail for one reason: the HDMI and USB cables for a single computer end up in different numbered ports. The fix is simple once you know the order. This guide covers how to set up a 4-port HDMI KVM switch the right way — power everything down, connect cables by matching port numbers, then boot and test each PC one at a time. The same process applies to current models such as the StarTech SV431DHD4KU and SV431HDU3A2, as well as the ATEN CS1794, so you don’t need a separate manual for every brand. If you’re still choosing a unit, our tested list of the best 4-port HDMI KVM switch options can point you to a model that’s easy to wire correctly.

The 4-Port KVM Setup Order That Works

Follow this sequence as written. It’s the order StarTech documents in its current KVM manuals, and it prevents the detection problems that come from hot-plugging cables in random order.

1. Power off all computers, monitors, keyboard, mouse, and the KVM itself.
2. Plug the console monitor into the KVM port labeled Console HDMI. On dual-display models, connect the second monitor the same way.
3. Plug the USB keyboard and mouse into the console ports, usually labeled Console or K/M. These are the ports used for hotkey control.
4. Connect each computer to its own port number: run an HDMI cable from PC 1 into HDMI port 1, then run a USB A-to-B cable from PC 1 into USB port 1. Repeat for computers 2, 3, and 4, keeping every HDMI and USB pair on the same number.
5. If you’re using audio, connect each computer’s audio cables to the matching numbered audio jacks.
6. Plug in the KVM power adapter, then turn on the KVM and the monitor.
7. Boot one computer at a time and confirm it appears on the monitor and that the keyboard and mouse respond. When the desktop shows up and the cursor moves, that port is wired correctly.

StarTech’s setup manual for its 4-port HDMI KVM switches spells out the same order, including the numbered port matching.

Hotkeys, Mouse Switching, and Keyboard Quirks

Once the cables are right, switching between computers is a quick key or mouse sequence. The keyboard and mouse ports on the console are dedicated to hotkey use, which is why some keyboards act oddly there.

Dedicated keyboard and mouse ports are intended for hotkey control, so a gaming or mechanical keyboard that isn’t detected should move to the USB 3.0 hub on the front panel.

Why Does a Port Stay Black?

A blank screen usually means mismatched cables, not a broken KVM. Check these in order.

• Confirm each computer’s HDMI and USB cables are in the same numbered port. This is the most common mistake, and it’s fixed by swapping one cable.
• Make sure the monitor is in the Console HDMI port, not one of the numbered PC ports.
• Boot only one computer at a time until video and input work, then move to the next port. This isolates any wiring problem immediately.
• For laptops, use a docking station that supports multiple graphics outputs if the laptop has only one HDMI port. ATEN’s CS1794 is documented for Windows, Mac, and Sun systems.
• If the keyboard or mouse doesn’t respond, move it to the front USB 3.0 hub before suspecting the switch.