Using VNC out of the box can be painfully slow. On one of my dual core Xeons it was taking 50% of the CPU!

Hunted around a bit and eventually found Peter’s article giving a solution.

The problem is caused by video hardware acceleration enabled graphics cards. I think it causes VNC to spend all its (and your) time taking screen shots and sending them down the wire. It makes VNC painfully slow.

So all you need to do is disable hardware acceleration:

1. Load the Control Panel.
2. Double click Display.
3. Click the Settings tab.
4. Click the Advanced button.
5. Click the Troubleshoot tab
6. Change the Hardware acceleration slider to None.
7. Click Ok.
8. Click Ok.

If the remote machine is a server you should probably disable hardware acceleration anyway, to give more power to the server. There’s no point using graphics hardware acceleration on a headless server in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying “Beware of the Leopard".

However, if you are using VNC to manage remote desktops then you might have to get your users to reduced the hardware acceleration before you start connect.