Some gp32s can only overclock slightly or not at all, because gamepark always try and find the cheapest providers of RAM available for each bach of gp32s, so sometimes they get lucky and get a supplier which makes good quality memory that can overclock. Overclocking requires more power from the gp32, so cheap or low batteries may not be able to handle the extra demand, so plugging in a power supply solves this problem, but only if the ram in your gp32 is able to overclock anyway.