Synchronous dynamic random-access memory

SDR SDRAM is Single Data Rate SDRAM, a type of computer memory. The term is used to contrast with Double Data Rate SDRAM, or DDR SDRAM, but since single data rate SDRAM was the only sort available when SDRAM was introduced, it is more commonly called "ordinary SDRAM" or something similar, rather than "SDR SDRAM".

SDR SDRAM comes in either 66mhz (PC66), 100mhz (PC100), or 133mhz (PC133) 168 pin DIMMs for desktops, or 144 pin SODIMMs mainly used in laptops.