1.9Ghz for sure.
http://www.cpuid.com/download/cpu-z-141.zip
That's a link to a cpu identification program if you're still lost
http://www.systemrequirementslab.com/referrer/srtest
This doesn't have an option to check for pirates though
Just because you meet it(system reqirements) doesn't mean it will run like a dream, try pressing F7 and dropping some of the graphics settings like the resolution, and some of the geometry settings down.
Lowering these values will increase speed of the game, and I find turning all reflection off makes sailing run like a dream.