1. First go to Tools> Preferences> Advanced> Network,
2. Select Server name completion.
3. Now you have two options within it;
Try name completion
Look For local network machine
4. If you uncheck both of the above options, i.e.; Try name completion and Look for local network machine, Opera will stop cycling your CPU, trying to guess what you’re typing in the address bar.
5. Restart the browser after applying the settings. You’ll see the speed difference.