I have a KVM switch hooked up to my Win7 box, and every time I switch away, it seems to disconnect the USB devices - keyboard and mouse.

Is there a setting somewhere to prevent this from happening?


I guess this is KVM switch specific. Some KVM switches emulate virtual keyboard, mouse and monitor for each computer it is connected to whereas some just switch away the connection without further processing. As all of us can guess, the switching type is much cheaper...

Not too much we can do here I believe...

  • Yes, it is KVM specific. I would look at different KVMs and use the vendor's return policy to cycle through them until I got what I needed. – RobotHumans Dec 14 '10 at 14:27
  • +1 -- This is a feature of the KVM switch itself. The only way to change it is by getting a different KVM. USB is designed to handle the disconnects/reconnects anyway, so it shouldn't be a problem in practice. At least, I've never seen it be a problem. Just don't go plugging an external HD or a flash drive into your KVM and you'll be okay. :-) – afrazier Dec 14 '10 at 14:30
  • i think what's troubling @chris is that it takes some time for the keyboard/mouse to initialise themselves on switching and it decreases productivity – bubu Dec 14 '10 at 14:32
  • Actually, the security monkeys force the VPN to disconnect for some reason. – chris Dec 14 '10 at 15:45
  • And there's one problem with this theory: when I switch over to my linux machine, there's no delay - the mouse & keyboard work right away, which leads me to believe that Windows is doing something. – chris Dec 15 '10 at 2:53

There are three types of USB KVM switch in the market now:

  1. USB Hub based KVM switch

    Cheapest one to make, simply just plug and unplug the physical USB cables to your connected systems. Most of the USB KVM switches in the market now are using Hub-based structure. Every time you switch ports, it will cause USB HPD (Hot-plug Detect) error/re-enumeration action for connected systems, specially for Windows 7 OS which checks the status of connected devices all the time.

  2. USB-emulation KVM switch

    One or two USB port emulated keyboard or mouse to every connected system.

    Pros: faster switching, Cons: doesn't work with most combos or wireless keyboards and mice, also some special functions of keyboards and mice will not work. It's okay for a non-Windows 7 OS, but will cause problems with Windows 7 because Windows 7's device stage does check and monitor devices connected to it all the time.

  3. USB-DDM (Dynamic Device Mapping) KVM switch

    Pro: Fastest switching without any USB HPD issue, 100% device mapping to all connected systems which maintains all the special functions of connected devices as long as USB HID devices, including touch-screen monitor, drawing tablet...etc. Cons: not many makers have this kind of switch and it costs more.


This worked for me:

  1. Device Manager > USB Root Hub > Properties > Power Management (tab)
  2. Uncheck Allow computer to turn off this device to save power.
  3. You can apply this to other devices under Device Manager > Universal Serial Bus Controllers
  4. You may need to restart computer for this to take effect.

For me, the effect was not immediate, but after 1 week or so, the switch speed has increased dramatically (2-4sec).

Sometimes, I still wait like 13sec, but after restart or unplug, everything works fast again.

Best regards!

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