Intel Haswell DDR3 Memory Performance Impact On Graphics

Across the range of frequencies tested, the Warsow Haswell performance was up by 19%.

Xonotic benefited quite a bit from the greater system memory bandwidth. DDR3-1333MHz memory is an absolute must for good performance on Intel Haswell CPUs but DDR3-1600MHz would certainly be recommended even for a low-end system and the cost difference in going for DDR3-1600MHz isn't much these days.