SDRAM, which is short for Synchronous DRAM, is a type of memory that synchronizes itself with the computer's system clock. Being synchronized allows the memory to run at higher speeds than previous memory types and asynchronous DRAM and also supports up to 133 MHz system bus cycling. Since 1993, this has been the prevalent type of memory used in computers around the world. In the picture below is an example of a SDRAM DIMM. The original type, named SDRAM, up to the current type, DDR3, are all derivatives of the SDRAM memory type.