The Geforce GTX 950 has a fair amount of overclocking headroom. However note that each sample overclocks differently and therefore our results can serve only as guideline for what you can achieve with another GTX 950.
The reference card’s base clock frequency is 1024MHz, with a boost clock of 1188MHz. However, The EVGA GTX 950 FTW base clock frequency is 1203MHz, with a boost clock of 1405MHz, and we measured clocks up to 1506MHz in games. This is already 179MHz overclock for the Base GPU clock and the GPU reached almost its headroom limit. We had two GTX 950 FTW cards and with one card we achieved +50MHz over the GPU factory overclock, while the second card allowed clock increase of only 10MHz. Note that this was achieved by using standard voltage and AUTO fan settings.
Memory overclocking was much healthier and on both card we raised memory clock by 350MHz (1400MHz effective GDDR5). Overal we measured up to 10% performance increase after our overclocking.