document updated 12 years ago, on Jun 14, 2011
A "modular KVM" is a cobbled-together combination of parts that achieves the same effect as a KVM. This allows you to tailor the functionality you want.
I frequently want to have MORE THAN ONE physical display (ala Synergy), but only one physical keyboard + mouse.
As my configuration progresses, I often end up having a separate switch for each feature (audio, keyboard/mouse, video), because usually I want independent control over each.
My computing environment
I often have at least three computers in my cube, and occasionally eight or more. The techniques described here allow you to usefully use many more computers than normally possible.
I usually label each computer #1 through #8, and then have each of my switches and cable-ends labelled the same.
I then have a "legend" that indicates which computer is currently attached to #1, #2, etc. Labelling most things with numbers instead of computer-name makes it easier to frequently add/remove computers.
Keyboard + mouse switching
Using USB is VERY preferable for two big reasons: 1) USB is capable of hot-plugging, PS/2 is not; 2) USB allows both keyboard+mouse to be carried over the same cable, PS/2 usually
[1] [2]
does not.
Switching options: (cheapest/dumbest at the top)
- Manually unplug keyboard from one computer, plug into another.
Requires a USB keyboard that has a built-in hub, with the mouse plugged into the keyboard, so you only need to move only one cable to switch both.
- Mechanical USB switch.
I like these the most, because they're super cheap and super durable. Cheap enough that you can buy several and combine them in various ways. They don't have keyboard hotkeys, but I almost prefer that, since USB switching is usually my last-resort fallback when Synergy isn't working, and I want my last-resort fallback to be bullet-proof.
- Digital USB switch.
Often just a KVM, without any video attached.
Given the quirks that KVMs have (often glitchy because they require their own keyboard/mouse drivers; some don't work with wireless keyboards at all), and the fact that I prefer to use Synergy 90% of the time, I really prefer mechanical USB switches as a fallback, instead of these.
- Synergy
It doesn't work for changing BIOS settings, or fixing boot problems, so having one of the others as a fallback is nice.
Video switching
Ideally, I wouldn't have to do ANY video-switching — ideally, each computer would have its own display. However, if you make that a hard-and-fast rule, then you end up limiting the amount of computers you can connect (or end up spending money needlessly), so I sometimes resort to video switching.
Often I want each individual display to have its own switch, so I can multiplex the computers that are attached to that one display, but leave all my other displays uneffected. This means that you REALLY want to have your keyboard+mouse to be on a completely separate switch, so the K+M switch is comfortable switching across separate physical displays.
Switching options: (cheapest/dumbest at the top)
- Monitor itself has an "input select" button.
I prefer ALL of my monitors to have this feature... usually it costs relatively little, and it's pretty convenient because it requires no extra space, and no extra (ie. messy) cabling.
- A dedicated VGA switch. (perhaps mechanical)
- Fancier video switch.
Often a 4-port KVM, without any K+M attached. DVI ones are substantially more expensive.
Audio switching + mixing
Merging the output of all computers is nice. It allows you to have your music collection playing from one computer but still hear alerts from the computer you're currently working on. It also lets you avoid having to change the audio-switcher every time you change the K+M switcher.
Switching options: (cheapest/dumbest at the top)
- solder audio connectors onto an old parallel/serial switchbox
- A mixer without any knobs/switches. The volume controls within each computer is the only way to selectively enable/disable each output.
- A mixer with one switch for each computer.
This at least lets you kill misbehaving software/hardware.
- A regular audio mixer.
Network facilities
Hopefully your workplace allows you to plug in a switch of your own, so you can plug in all of these devices. If not, NAT may be required (probably via a configurable router).
- clipboard sharing
- dynamic DNS (DDNS)
This is awfully handy, and is practically required if you do much VM work. Triggering off of DHCP option 12 is a great way to make DDNS work across Linux and Windows alike, without having to configure ANYTHING on each client.
- file sharing
I don't know, I haven't found a convenient way to do this yet.