How to make the hottest CPU temperature?
You should check out the venerable cpuburn app http://patrickmylund.com/projects/cpuburn/ and a quick google also showed there is a CPUBurn-in app for windows and linux http://cpuburnin.com/

I know cpuburn had special switches to turn on platform specific instructions for getting the maximum heat out and since the source code is readily available under the liberal MIT license, you can just peek at the code your self.