If you have the NA DEM map loaded in your 3490 you will see that there is dem shading overlaying your detail map but just be sure you have it enabled in Map Layers. If you compare the 2595 and the 3490 at the same point on a map [preferably pick someplace rural] then you will see the difference at normal zoom. The 2595 will only display dem shading when zoomed right out and then it's the shading from the basemap which is showing.