Two-Port KVM

• You can switch two computer inputs with a two-port KVM. You use one monitor, keyboard and mouse on two computers using the USB port and switch using a manual switch, hot keys or dedicated KVM software. These two-port devices have greater use in the office than in the server room, where you might need to switch between more than two servers.
  
  Usually, the video part of a two-port KVM switch is managed by three or more VGA DB 15-pin connectors. Two route to the two video sources, computer 1 and computer 2. The central VGA goes to the monitor. When mouse and keyboard are also switched, they can be switched via two-by-four-pin Type A USB connectors. PS/2 devices can either be switched through a PS/2 interface or via a PS/2-to-USB adapter, which is a 4-inch wire with PS/2 sockets for mouse and keyboard on one end and USB at the other. Normally, these devices do not require any form of external power supply. Many of these devices also share the switching of audio.
  
  

Applications

• You can multitask with a KVM, such as finding solutions for a computer on one port of the KVM while looking for the solutions on the other port. You can also build a Linux server using one port while browsing for solutions on the other one. You can switch between machines at any time you want, even while the machines are booting up. If the KVM has a DVI connector, you can switch between Apple Macintosh computers and PCs, too.
  
  

Disadvantages

• KVMs are quite variable in their quality between manufacturers. Even reputable manufacturers like Belkin, TrippLite and Hawking can have issues, mainly with USB KVMs. Previously, when a KVM switched either VGA or VGA and PS/2 channels, there was never a problem of synchronization. Now that KVMs have USB ports to switch, there is a small lag between connections using USBs. Not all KVMs suffer from this. A manufacturer called Iogear has a patent on USB emulation technology that stops the disconnect/reconnect pattern experienced by USB peripherals when switching in other low-end and even high-end KVMs. Using an IOGear device, both devices are still connected on the input, and it is the output that is switched, avoiding problems with synchronization.