CPU-Control is a free tool that allows you to manage how those applications are using your processors. You can choose if an application will use one or various processors at a time.
CPU-Control also lets you choose which processor will run each process, so you can distribute a task between both. You can even create profiles with this information, to easily assign a task in the future.
You can also use the program to move the system load to one sole processor, and decide which of the two it will be.