a = 1000000;
Plot3D[x y/a, {x, -10, 10}, {y, -10, 10}];

<< RealTime3D`
Plot3D[x y/a, {x, -10, 10}, {y, -10, 10}];

<< Default3D`
Plot3D[x y/a, {x, -10, 10}, {y, -10, 10}];