In terms of Memory Size a SDRAM (Synchronous Dynamic RAM) chip has 168 pins in its memory module. Alternatively, DDR -type memory modules have 184 pins.
In terms of Transfer Rate a DDR (Double Data Rate SDRAM) memory can transfer data at a rate of 333 MHZ with its dual-module-designed chip (166 MHz x 2). SDRAM chips transfer data at a single rate of 133 MHz.
The Required Voltage are SDRAM originally requires 3.3 volts to function properly. DDR RAM memory chips need only 2.5 volts.
The 184-pin DDR RAM-type memory has replaced the 168-pin SDRAM and is suited for computer processors that are 1GHz or higher. The 168-pin SDRAM memory chip is not included in newly produced PCs (since 2007) and was used with processors lower than a gigahertz.
SDRAM chips are associated with PC66, PC100 and PC133 computer standards. DDR RAM chips work with PC2100, PC2700 and PC3200 computer standards.