Preheat oven to 350 degrees; pour peaches with syrup in pyrex pie dish; sprinkle cinnamon on top of peaches; sprinkle all of cake mix proportionately over peaches; cut butter in thin squares and layer in rows on top; covering the surface, use all the butter.
Place in oven and bake for 1 hour or possibly till top is brown.
(Oven temperatures may vary, time can be adjusted from 45 min to 1 hour.)