A KVM switch allows multiple computers to share common peripherals such as the computer's keyboard, mouse and display or monitor. They come in many shapes and sizes and deciding what type and size needed for your situation can be confusing if you do not know the features and connection types available.

It all starts with the ports

Usually KVMs are described and retailed by the type and port numbers available. A 2 Port KVM Switch will support up to two computers sharing the peripherals and a 4 Port KVM Switch will support up to 4 PCs sharing the peripherals.

KVM Types

In order to understand the various types of switch available, it is necessary to split them into two groups, commercial and home user. The commercial KVM switch boxes usually have 4, 8 or 16 ports and are usually used to control multiple server systems with one keyboard, mouse and monitor. These can be chainable and expandable making upgrading capacity for future PCs or servers a simple task.

There are also commercial systems available that are bought as modules. There will be software or a control box that allows switching between server systems and runs over existing network cabling making it simple to roll out across large server rooms. These systems are referred to as CAT5 KVM Switches.

Home user systems usually come as 2 port KVM switches. They allow two PCs to share common resources and are usually required as a space saving device. It is also much cheaper to buy a KVM than purchase a second keyboard, mouse and monitor. Why you would need one at home is debatable but they can be useful.

It may be that you have computer used for gaming and another for business or office work. Using a KVM in this situation would make sense. Another use for 2 port KVM switches is when you have a desktop and a laptop PC. By using a KVM it is possible for the laptop to use the resources of the PC without the need for unplugging all the required peripherals that would require the desktop to be powered down.

How do they work?

In a home user 2 port KVM switch scenario, the switch box is connected to a spare USB port and / or the PS2 connectors used for older keyboard and mouse connections. A cable will also be connected to the computers display or video output. This is repeated on the second machine that is to share the devices. The keyboard, mouse and monitor are then connected to the 2 port KVM switch allowing them to be shared by both computers.

Depending on the type of KVM being used, there may be a number of buttons on the switch to allow simple switching between the two computers. Some KVMs come with software which once installed, allows keyboard shortcuts to be used to switch between the PC units.

Commercial systems are very much scaled up versions of the home user KVM switch except for the CAT5 systems which require a small switch device connecting to the ports of the PCs / Servers and a CAT5 cable chain each one together. These devices can then be accessed either by a control box or across the computer network making management a much easier task.

Final Note

When purchasing 2 port, 4 port or larger KVM controllers you should always allow for expansion if you think you may need it. Are you likely to need peripheral sharing capacity for more devices in the future? This is especially important in commercial setups.

It is also very important to note the type of ports required by the connecting devices. The older PS2 keyboard and mouse connections on PCs are slowly on the decline, many servers and desktop PCs come without the older connector and rely on USB for keyboard and mouse connectivity. If you have a mixture of devices you may need multiple KVM switches to meet your needs.

Video connectors have also changed over the years with DVI-D now common on a lot of PCs. All these ports and connectors need to be carefully considered when researching and purchasing the different types of KVM switch.