Africa.dem
SRTM data V3, 2006, International Centre for Tropical Agriculture (CIAT) [Only registered and activated users can see links. ]
If the problem is space and machine resources use this.

South Africa.dem
[cgiar]DEM_SouthernAfrica-HiRes_CGIAR_0606
Hole-filled seamless SRTM data V3, 2006, International Centre for Tropical Agriculture (CIAT)
Available from [Only registered and activated users can see links. ]
~SAF|2006.06||Premium|
It is recommended if you prefer a more realistic driving.

Read with [Only registered and activated users can see links. ]