Differences in Memory Speed and Data Rate

by Crucial Employee on ‎01-12-2016 01:40 PM - edited on ‎07-14-2017 08:52 AM by Moderator Moderator (2,999 Views)

Question

What is the difference between DDR3-1333 (PC3-10600), DDR3-1600 (PC3-12800), DDR4-2133 (PC4-17066), and DDR4-2400 (PC4-19200)?

Answer

Although these are all types of double data rate (DDR) memory, the varying numbers refer to the different speeds of memory, and even different memory generation types. When looking at the Data Rate (DDR), or speed PC (Per Clock transfers), it is important to note that systems can only handle certain types of memory - this is why it’s important to use either our Crucial Memory Advisor or System Scanner, when looking for compatible memory to install in your system.

 

It is easy to get data rate and speed mixed up because they are often interchangeable when someone is talking about how “fast” memory is. In layman’s terms data rate is how many bits a module can transfer in a given time, and speed is how many bytes it can transfer. Since there are 8 bits in a byte, we simply multiply the data rate by 8, and get the speed of the memory: 1600x8=12800, 2400x8=19200, where these results are your transfer rates in Megabytes per second (MB/s). When looking at both the data rate and speed, the particular generation of memory will be listed as well - for example PC3 prefaces DDR3 speeds, and PC4 prefaces DDR4 speeds.

 

Below is a list of common memory speeds and associated data rates. There may be some higher- and lower-end speeds that are missing, and slight differences depending on how numbers are rounded, but it is a good general overview of common memory performance attributes.

 

Data Rate

Speed

DDR2-667

PC2-5300

DDR2-800

PC2-6400

DDR2-1066

PC2-8500

DDR3-1066

PC3-8500

DDR3-1333

PC3-10600

DDR3-1600

PC3-12800

DDR3-1800

PC3-14400

DDR3-2000

PC3-16000

DDR3-2133

PC3-17000

DDR4-1866

PC4-14933

DDR4-2133

PC4-17066

DDR4-2400

PC4-19200

DDR4-2666

PC4-21300