In the cube $ABCD - A_{1}B_{1}C_{1}D_{1}$ , let $E , F$ be the midpoints of $CD , A_{1}B_{1}$ respectively. The total number of intersection points of the sphere with diameter $EF$ and each edge of the cube is $\_\_\_\_$ .
In the cube $ABCD - A_{1}B_{1}C_{1}D_{1}$ , let $E , F$ be the midpoints of $CD , A_{1}B_{1}$ respectively. The total number of intersection points of the sphere with diameter $EF$ and each edge of the cube is $\_\_\_\_$ .