Single memory module means missed computing opportunity

Using just a single memory module in a computer will sacrifice performance, because most computers need a pair of them to go into dual-channel mode. Sticking to a single RAM module means staying in the single channel mode, which cuts data transfer rates in half.
It also means the entire computer's processing power is reduced and slows down the processor's integrated graphics. That means two 2 gigabyte (GB) modules are better than a single 4 GB module. Similarly, two 4 GB modules are better than one 8 GB version and so on. To work effectively, the two modules have to be of the same size and manufacture.