5 votes

What's the best way to connect four monitors to two computers?

I will spare you the life story of how I came to want to do this and instead outline what I would like to accomplish:

  • One (Windows) desktop computer with a video card that has two HDMI and two DisplayPort ports.
  • One (Linux) laptop that has two USB-C Thunderbolt 3 ports.
  • Four monitors:
    • 1920x1080 60Hz
    • 2560x1080 75Hz
    • 3440x1440 100Hz
    • 5120x2160 60Hz

What I would like to do is connect all four monitors into a KVM switch, and then from the KVM switch, connect all four monitors to both the desktop and the laptop. I would also like at least one USB port on the KVM that I could connect a USB hub to for switching my mouse, keyboard, graphics tablet, etc.

From there, ideally I would be able to switch all four displays and all the peripherals between each device by pressing a single button on the KVM.

However, there are three problems I have encountered with this idea:

  • KVM switches are expensive as fuck
  • Very few KVM switches support a two-computer, four-monitor [2x4] connection (it is almost always the other way around [4x2])
  • The few KVM switches I have found that do support such an arrangement only have DVI ports, no DisplayPort or HDMI

So uh, if anyone knows of any KVM switches (or other solutions) for accomplishing this setup, I would really love to hear about it, no matter the cost.

Thanks.


In this setup, the laptop would be the daily machine, and the desktop would be a dedicated gaming/creativity rig. That gives me some room for alternative configurations:

  • Because the desktop wouldn't really need access to four monitors, I could get a KVM switch that only supports two monitors [2x2], and then just use something like Synergy to seamlessly move the mouse and other peripherals between computers. However, I have concerns with how well Synergy would work with a custom mechanical keyboard (running the QMK firmware) (Apparently there are no issues between QMK and Synergy)

  • Buy two [2x2] switches, which is probably cheaper than one [2x4], and switch all four displays between devices with two button presses instead of one. (And still probably run Synergy for when I want to split displays 2/2 between devices)

  • Just use a Thunderbolt dock, plug each monitor into the desktop and also into the dock (so two cables coming out of each monitor), and just manually switch the monitors between devices using their input controls. This is probably the simplest option, but switching four monitor inputs can be tedious. Though, I wouldn't actually need to switch all four of them, I could just switch one or two of them, and then use Synergy to take advantage of the others.

  • Run the desktop headless and stream its video output over the local network to the laptop/monitors. This might actually be the cheapest solution, but input latency would be variable with network conditions and could be a concern. I would also be dependent on specific services for streaming output. Parsec would be my go-to. I have used it before, including with friends over 1,000 miles away, and it works great. However, I'm not too keen on my computing setup being dependent on a single (proprietary) service.

4 comments

  1. [2]
    Akir
    Link
    Since this is a no expenses barred conversation, theres a pretty easy solution; buy a killer good laptop and get rid of the PC. If you want separate working environments, either set up a second...

    Since this is a no expenses barred conversation, theres a pretty easy solution; buy a killer good laptop and get rid of the PC. If you want separate working environments, either set up a second account or virtualize.

    It's probably not the answer you were looking for, but I think it's probably going to be the easiest one to deal with overall.

    3 votes
    1. hungariantoast
      Link Parent
      That's certainly an option, and then I could just dual-boot between Windows and Linux when I want to switch gears, or set up VFIO... Which is exactly what I'm doing on my desktop now! No seriously...

      That's certainly an option, and then I could just dual-boot between Windows and Linux when I want to switch gears, or set up VFIO...

      Which is exactly what I'm doing on my desktop now!

      No seriously though, this is something to consider, thank you.

  2. [2]
    patience_limited
    Link
    I've had to deal with similar problems for radiologists that are reading at multiple hospitals, with each hospital system (and its associated software and tools) on separate PCs. We were using...

    I've had to deal with similar problems for radiologists that are reading at multiple hospitals, with each hospital system (and its associated software and tools) on separate PCs. We were using this.

    It's hard to get a reliable quad-head KVM for under $1,000, for starters, and you've got to use DisplayPort if you want to support 4K resolution at 60 Hz refresh. You'd also need to convert your USB-C laptop output with a dock.

    The two [2x2] switches are probably your best option if you want to keep costs under control. Nonetheless, all of these solutions except the Thunderbolt dock are going to have too much response lag for gaming, and I can guarantee you'll see weird bugs with a custom keyboard.

    1 vote
    1. hungariantoast
      (edited )
      Link Parent
      I hadn't even thought about latency. I don't play competitive shooters or anything strenuous like that very often, so it might end up not being an issue, but it is something to think about. Thanks...

      I hadn't even thought about latency. I don't play competitive shooters or anything strenuous like that very often, so it might end up not being an issue, but it is something to think about. Thanks for pointing that out.

      As for the keyboard stuff, I actually think I will be okay. I was doing a bit of reading and people don't seem to encounter issues between Synergy and the QMK firmware. Apparently Synergy acts as just a "dumb lane" for keyboard input, which is exactly what it should do, and that means that keyboard input is sent unmodified between devices. KVM switches also should just be "dumb lanes" so I think I'm golden?

      Like you said, two [2x2] switches are probably my best option, but if input latency is too bad to ignore I might end up just using a Thunderbolt dock.

      However, there was one other thing I didn't think about when writing alternate solutions last night:

      Run my desktop headless, and stream its output to the laptop. That probably sounds terrible at first, but everything will be plugged into the same network and I bet the input latency actually would not be that bad.

      1 vote