KVM switches (Keyboard, Video, Mouse) allow one keyboard, video monitor and mouse to control multiple computers.
Simple 2 port consumer KVMs ($20 to $100) are available for home use. Rackmount KVMs with over 4 ports (a few hundred to over a thousand dollars) are used in corporate IT departments and data centers.
Popular brands include Belkin (Flip, OmniView), Iogear (MiniView Micro), Aten, Avocent, Raritan, Startech, Switchview and Linksys (ProConnect).
KVM Versus Remote Control Software
Remote control software such as VNC work only after the operating system has booted up. A KVM works at all times:
- Allowing changes to BIOS settings.
- Allowing control of dual-boot machines.
More sophisticated KVMs can remotely power up and down computers, resetting "hung" or crashed (BSOD) machines. This is especially useful for KVM over IP, where direct physical access to the computer is not available.
Some KVMs can remotely mount USB CD/DVD drives, allowing remote installation of software from optical media. However, booting from a remote drive is not often supported.
Home or Consumer KVM
Home users need to check that the KVM has the right ports for their video monitor, keyboard and mouse.
Simple computers work best:
- Low to medium resolution analog VGA displays (though shadows or ghost images can plague analog VGA KVM connections).
- PS2 keyboard and mouse.
More likely to have compatibility issues are:
- Digital DVI displays.
- High resolution VGA displays (above 1024 x 768 pixels).
- USB keyboard and mouse, especially those that share one USB connector.
- Wireless keyboard and mouse.
- Multifunction or programmable keyboard shortcuts or hotkeys.
- Wheel and other advanced mouse.
- Notebook docking stations.
Due to the large variety of computer hardware and software (drivers) in the market, it is best to "try before buy" or to buy from a shop with a good return policy. This is especially true when using non-Windows systems such as Mac, Sun and Linux.
Additional items or features to consider include:
- Cable length. Connecting cables are often short, meaning that the computers need to be close to each other and to the KVM.
- Remote switch. Some KVMs have a simple click control switch on an extension cord. This allows easy switching while keeping the KVM hidden under the desk.
- Keyboard switch. Some KVMs can be switched from the keyboard. Sometimes, special software needs to be installed in the PC to enable this function, sometimes not.
- Audio speaker and microphone ports. Some KVMs allow these ports to be switched independently, allowing the user to work on one machine while listening to music (through the KVM and connected to external speakers) from another.
USB KVM
KVMs that support USB keyboards and mouse are sometimes powered from the computer's USB port. This is convenient as a separate power connection is not needed.
However:
- Some computer ports might not be able to provide enough power.
- The computers might need to be switched on in a fixed sequence, as the KVM draws power from only one computer.
Rackmount KVM
Corporate data centers will want a rackmount KVM to conserve space, together with a rackmount video monitor and keyboard. A sliding 1U rackmount video monitor and keyboard (without a KVM) can cost over a thousand dollars.
With the larger number of computers controlled (8 to 64 with one KVM, advanced KVMs can be joined up by daisy-chaining or cascading to control even more computers):
- A programmable (names of computers can be customized) on-screen menu to select each computer is necessary.
- Cables are often purchased separately. They can be expensive and significantly add to the total cost.
Security is more of a concern in corporate environments, so rackmount KVMs are usually password protected.
KVM Over IP
KVM over IP systems combine the worldwide Internet reach of remote control software, together with the boot control (BIOS change, dual-boot) of a KVM.
They are password protected and connected over the Internet via an encrypted protocol such as 128 bit SSL. Some need a custom software client, which can be downloaded directly from the KVM.
They will never be as secure as a hardwired KVM and should not be used for high security installations. The contents of the graphics screen needs to be sent over the network, so screen updates can be slow.
CAT5 and Other KVM Extenders
KVM extenders are in between standard KVMs and KVM over IP. Their range is a few hundred feet, good enough to reach almost anywhere within a building.
CAT5 KVM extenders use standard CAT5 UTP network cables and RJ45 connectors but otherwise don't run over IP networks.
The Best KVM
For home use, port compatibility (USB or PS2, VGA or DVI) is the main concern.
Enterprise IT departments need to worry about the number of ports for future expansion (or daisy-chaining, cascading) and security.
KVMs are not without issues. If switching delays and video compatibility are causing problems, or the number of computers is large, a purely software remote control solution can be a better choice.
Yuen Kit Mun - Kit Mun is a self-confessed information junkie, reading an average of a book a week over the past two decades. His growing Internet ...
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