Depends on a couple of things, if the mobo chipset supports more DRAM, if the CPU (or onboard MC 9memory controller with older mobos like socket 775) can handle more, and if those conditions are met if the BIOS has been programmed (updated) to accept more than the original specs call for. It's seen occasionally but not often, i.e. some 1366 mobos can actually read and utilize 8GB sticks though the original mobo specs was to 4GB for sticks