All of the 512MB SDRAM & 256MB "High Density" modules we sell are built using 'High-Density DRAM' technology. Your system's motherboard must accept 512MB in each memory slot & 1.5GB or more system memory in order for these modules to work properly. In the event that your motherboard does not accept 'High-Density' SDRAM, you system will either show the memory module as a smaller size (i.e. 256MB or 128MB) or will not read it at all. The best way to know is to consult your system/motherboard documentation or the manufacturer's website.