One of the main differences between DDR, DDR2 and DDR3 is the highest transfer rate each generation can reach. Below we list the most common speeds for each generation. Some manufacturers can deliver memory chips capable of achieving other speeds than those listed; for example, specialty memories targeted to overclockers. Clocks ending in 33 and 66 MHz are, in fact, periodic decimal expansions (33.3333 and 66.6666, respectively).

Memory Real Clock Maximum Theoretical Transfer Rate Memory Module
DDR200 100 MHz 1,600 MB/s PC-1600
DDR266 133 MHz 2,133 MB/s PC-2100
DDR333 166 MHz 2,666 MB/s PC-2700
DDR400 200 MHz 3,200 MB/s PC-3200
DDR2-400 200 MHz 3,200 MB/s PC2-3200
DDR2-533 266 MHz 4,266 MB/s PC2-4200
DDR2-667 333 MHz 5,333 MB/s PC2-5300
DDR2-800 400 MHz 6,400 MB/s PC2-6400
DDR2-1066 533 MHz 8,533 MB/s PC2-8500
DDR3-800 400 MHz 6,400 MB/s PC3-6400
DDR3-1066 533 MHz 8,500 MB/s PC3-8500
DDR3-1333 666 MHz 10,666 MB/s PC3-10600
DDR3-1600 800 MHz 12,800 MB/s PC3-12800

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.