What speeds does DDR come in?
DDR SDRAM comes in two speeds: PC2100 and PC2700. (PC1600 has been replaced by PC2100, which is backward compatible.) Despite what these names imply, DDR is twice as fast as PC100, not roughly twenty times faster. PC100 SDRAM modules have a bandwidth (the amount of data they can move) of 0.8GB/sec. Since DDR SDRAM can move data twice as fast as SDR SDRAM, 266MHz DDR SDRAM (133MHz doubled) has the bandwidth of 2.1GB/sec and is referred to as PC2100.
